Hi,
And welcome to this week’s deep-dive into all things fermented and tasty, thank you so much for joining me.
In this newsletter I wanted to share my absolute masterclass in miso making, the most profound ingredient for flavour and health in my day-to-day cooking, along with some tips on how you can level up your miso making skills. So welcome back, get your cup of tea, and brace yourself for my most in-depth miso masterclass, where we explore all things flavours and food that money can’t buy.
Topics:
Chef’s Almanac - Field Beans
Introducing Koji
In Search of Umami, A Miso Deep-Dive
Store Bought vs Homemade Koji
A Summer Miso Recipe for Home Kitchens
One Half of an Immortal Bread Roll
Chef’s Almanac - Field Beans
Harvested in August
This week saw the harvest of all our field beans, a crop usually grown as a green manure, that we found fills a gap in the season between fava and runner beans. We also grow a culinary variety called Vespa, which is similar to a small fava bean, about the size of large chickpeas. These pale grey-green beans are delicious. Nutty, earthy, sweet, with a hint of bitterness. The tops of the plants are a tasty alternative to spinach in recipes, providing a halfway point between pea shoots and leafy greens, and the flowers and smaller pods are edible whole. The small pods in particular are wonderful fried in a light tempura batter, whilst the flowers make for a sweet, nutty, slightly silken tofu tasting addition to raw salads.
I usually process our bean harvests three ways each year: Blanch and freeze, dehydrated and salted, and my favourite, mashed into miso.
Some years ago, I started making my own miso as a means to use up and preserve bumper crops of peas and beans. It’s one of my favourite things to make with heirloom varieties (besides eating them raw, straight off the plant), transforming them into rich, fruity, umami fermented paste packed with digestive enzymes and nutrients that forms the bedrock to a lot of recipes. Making miso takes the humble bean or pea, mixed with koji rice (a rice that’s had a specific beneficial mould grown on it, most often Aspergillus Oryzae), and salt. Left to ferment for 3-12 months, depending on the recipe, miso turns a bean into something more potent, complex, and flavoursome than most stocks.
But how?
Introducing Koji
Koji is the name given to an ingredient, usually grain or legumes, used to grow a specific mould, Aspergillus Oryzae. The combination of these together is called koji, a word from the Japanese language, where the fungus holds a special status as the national fungus of Japan, with thousands of years of influence over every detail of Japanese cuisine. If you’ve ever enjoyed soy sauce, miso, mirin, sake, amazake, shoyu, or more, then you’ve experienced the tastebud tingling umami and refreshingly complex sweetness of koji.
In recent decades, koji has slowly taken over the world. Transforming from the often sacred traditions of Japanese cuisine, and the cuisines of the entire East Asian world, to the radically experimental cuisines of Europe, where the mould has revolutionised our approach to food waste, flavour, bioavailability, and nutrition. Most people outside of the world of food might not realise that the currents of change taking place in their own cuisines rival that of the invention of blue cheese and brie, both of which are also results of a different set of moulds belonging to the Penicillium genus.
But what makes koji so powerful?
Aspergillus can produce a prolific variety of enzymes (proteins that can break down molecules and form new ones). What this means is that no matter what ingredient we grow the mould on, it can unlock nutrients and flavours that our own digestive system and entire gut microbiome cannot.
Outside of the world of food, Aspergillus is responsible for the ‘bio’ part of biological detergent, having first produced the enzyme that’s now synthetically added. Two close relatives in the Aspergillus family were even discovered digesting plastics in as little as 140 days. It’s a pretty useful microorganism. Having found its way into many industries and ways of life since its domestication thousands of years ago, taking it all over the world, into climates and countries it would otherwise never have reached, one has to ask, who has domesticated who?
If you’re interested in making miso but aren’t sure about growing your own koji, you can buy rice koji online from a number of producers. In the UK we have The Koji Fermentaria SousChef, Umami Chef, or Koji Kitchen. You can also track down international suppliers through Amazon (which I use to find them, then make my way to their website and buy directly). If you’re interested in making your own koji at home then let me know and I’ll post a dedicated recipe for how you can make koji safely and reliably in my home kitchen.
In Search of Umami, A Miso Deep-Dive
Making miso is a different approach in fermentation. For starters, it’s a solid state fermentation, much like cheese. It’s also a form of secondary fermentation, meaning the main growth stage has already taken place on the rice koji, which takes 48 hours, and now it’s simply a case of mixing this rice with cooked bean mash and salt. During its growth cycle the koji has loaded the rice with enzymes which it used to break into the grain and grow. Now the mould has been stopped by cooling and drying the rice out, but its enzymes are still very much active. By mixing it with cooked beans, we create a medium where these enzymes can act upon the molecules of the beans, breaking down starches into sugars and protein into peptides. The latter being responsible for the flavour we experience as umami.
The beauty of miso is the way enzymes work. Unlike the industrial manufacturing of sugars and amino acids, which produces a uniform molecular structure, and a one-dimensional flavour. Koji’s enzymes are pure chaos. They bump around breaking proteins and starches down into random lengths of molecules, which we experience as different layers of umami and sweetness. But it doesn’t stop there. Koji is often said to be a ‘facilitator’ of other microbes, meaning it provides conditions for microbes such as lactic acid bacteria (responsible for sauerkraut, kimchi, yoghurt etc) and yeasts. These then provide additional layers of flavour with their own enzymes and byproducts like lactic acid and ethanol. Pretty cool, no?
I’ve been making miso out of every bean and pea I can get my hands on and testing the results. Using homemade and premade rice koji, different substrates (rice, barley, oats, rye, spelt), different temperatures at different times of the year, harvests, and moisture / salt content. I also want to take this opportunity to give my thanks to my incredible koji master, Haruko Uchishiba from The Koji Fermentaria, who has taught me so much.
Before we jump into how you can make your own beginner friendly miso at home, I wanted to cover a quick note on using store bought koji vs homemade, as store bought is likely to be what most people go with for their first time making miso.
Store Bought vs Homemade Koji
You can make miso without needing to know the details, timings, temperature, and humidity for all the intricacies of growing aspergillus. Much in the same way you can make wine using a sachet of yeast, miso becomes incredibly straightforward using a premade koji, and it’s certainly not something to turn your nose up at. Will it ever be as good as the perfect homemade koji and miso? No, but it’s still often much better than the miso on offer in shops and a lot cheaper too. It also serves as a great way to process a large amount of beans and peas without much forward planning.
The pros
Very quick and easy
Ready to use straight away
Lasts a long time when stored correctly
Often easier to source than spores
The cons
A lack of control of the exact outcome
Harder to make a smooth final miso
For the following recipe, I will outline steps I take that are different depending on which I use.
But before we jump into the recipe, if you’re new to my Substack, please consider subscribing. I’m on a one-man-mission to make fermentation and great food as accessible as possible to everyone, and I’d appreciate it if you decided to join our little community by clicking the link below.
Summer Miso Recipe
There are two main types of miso, winter and summer. Working with the seasons, we can make a fresh summer miso that’s ready to eat in just 3 months (with the scope to age up to 6 months). For this recipe you will need rice or barley koji. If you don’t make your own fresh koji, you can source rice koji online from a number of suppliers (listed above). This koji is made in bulk and dehydrated to preserve for a long period of time. But this makes it harder to mix into a smooth miso. To make a smooth miso you’ll need to empty it into a clean bowl after 1-2 months of fermentation and crush it by hand again now that the rice has rehydrated from the moisture of the beans and the koji enzymes have had time to break down the starches.
Ingredients
500g fresh beans*
500g rice koji
100g salt
* Use 250g in dried weight and soak overnight before cooking them. This should give you 500g of cooked peas.
Method
Cook the fresh beans in boiling water for 3-5 minutes, until they’re soft to crush. This should take less than 300g of pressure if crushing one against a set of scales. If using dried beans, soak them for 6-24 hours, then cook them until soft. Cooking times will vary depending on the bean variety, and you can use a pressure cooker to shorten this time. As a general rule of thumb, every 10C over 100C will half the cooking time required. Reserve some of the water from the cooked beans for later.
Once the beans are soft, mix the rice koji with the salt to break up the koji, then use a potato masher or meat grinder to crush the beans. This doesn’t have to be a smooth mash, keeping some bean piece intact makes for a nice texture in the final miso.
Combine the cooled bean mash with the koji and salt and mix well.
The resulting mash should be soft and malleable and stick to the bowl when thrown. If it cracks when pressed then it's too dry and you should add a small amount of the aquafaba (cooking water) we saved from earlier. Add a tiny amount at a time as you don’t want to over saturate the miso. If it releases water when squeezed then you’ve added too much. This is a problem as the excess water will cause the miso to turn alcoholic and develop unpleasant tastes. Whilst the most ideal situation is to avoid adding too much water to begin with, you can remedy this by adding a small amount of flour or gram flour to the miso and mixing it in. However, the miso will develop a different taste.
Note: when adding water, as the salt percentage is quite high in miso and the amount of water we may need to add is so small, you don’t need to worry too much about adding extra salt.
Pack the miso into a clean, sanitised crock or jar by rolling it into palm sized balls and pressing them firmly in, one at a time. Your aim here is to avoid trapping air between the layers and provide no cracks that could allow mould to grow throughout the mixture.
Once all the miso is packed neatly into the jar, widespread technique dictates that we sprinkle additional salt over the smoothed top, then apply a weight equal to half the weight of the miso. However, I don’t do this anymore. Instead, I lay a round piece of greaseproof paper over the surface, pressing it in contact with the miso so that no air is beneath it, then squeeze a blob of fresh wasabi paste on top. Wasabi and horseradish both give off a specific chemical that is anti-mould, the very same chemical that makes your nose tingle when you sniff them. By adding a small amount on top of the miso, we can stop all unwanted mould from growing far more effectively than the salting method. Read below to find out more on how and why this technique works and what I’ve done to test it.
Once the wasabi is in place, cover the top of the jar with a layer of plastic wrap, then pop the lid on top. Remove the rubber seal, as we want the jar to be able to let carbon dioxide out, but secure the lid over the layer of plastic wrap. This will trap a pocket of wasabi gas in the top of the jar and prevent pathogens from growing.
Store the jar somewhere cool and out of direct sunlight for 3-6 months before tasting to see how it’s developing. I find that fava and butterbean misos go through a light, buttery, umami stage before entering a darker, richer, fruitier stage from 6-9 months. Beyond that, this recipe develops cheesy notes, sometimes even forming tyrosine crystals (similar to aged cheeses and meats).
Once fully aged, the miso can be stored in a fridge to preserve the best flavour and consistency, or continued to age at room temperature as it has been for the prior 6-9 months.
Uses: You can add a teaspoon of miso into anything that requires seasoning, both sweet and savoury. Miso mash potato is amazing, where the butter in the mash carries the savoury, fruity umami throughout the mash. Miso caramel is on all the fancy menus these days. Miso and lemon salad dressing is a game changer for all salads. And miso mixed vegetable pie is quite the centrepiece if you’re feeding friends and family and want to give them a real treat. You can also make an incredible compound butter by mixing 1tbsp of white miso with 400g of unsalted butter, to use in cooking, or to make the best sandwiches, toasties, and garlic bread you’ve ever had. See my previous post for a delicious and simple miso broth recipe that you can use with any and all of your homegrown vegetables. Whilst miso does have a high salt content, it’s important to note that you rarely need much of it to impart incredible flavour to your meals.
Additional step for store bought rice koji:
You may notice that as the miso ages, the rice koji bits remain quite solid. The same is sometimes true for unshelled beans, where the skin can retain intact for a long time. In both cases it is perfectly acceptable to open up the miso jar after 1-2 months and re-mash it. At this point the moisture, enzymes, and acids have had time to soften everything up, making it much easier for you to make a smooth, homogeneous miso. Once mashed, repack it again and top with fresh wasabi.
Note for longterm miso ageing:
If you’ve made a winter miso which ages for a minimum of 12 months, as temperatures increase over summer, you may find the wasabi runs out of power. This can leave the miso vulnerable to mould on the surface. In this case, I tend to replace the wasabi every 4-6 months.
One Half of an Immortal Bread Roll
Often, a freshly made batch of miso is topped with additional salt and weighed down with ceramic or stone weights, but the salt only slows mould down for so long. By the time the miso is ready, there is usually a thick layer of at least 2-3cm (1inch) or more of miso that has to be discarded, which can be disheartening and sometimes a little off putting, especially if you’re new to fermentation. This waste is even more painful if, like me, you’ve grown the peas or beans yourself, spent hours podding them, and know just how many minutes of life you’re throwing away with every mouldy spoonful.
Some time ago, I was having a catch up and making miso with my mentor and friend, Haruko, owner of The Koji Fermentaria and she showed me a little trick that she uses in her practice. With a knowing smile, she cracked open a crock of aged miso that was 9 months old, that had no additional salt or weight on top. The surface was smooth, glossy, and completely free of signs of spoilage. In the centre of the miso was a small piece of greaseproof parchment, and laying in the middle of this, was a small, bright green worm. Wasabi paste.
As it turns out, there is a specific chemical given off by plants like wasabi and horseradish called Allyl isothiocyanate which gives them their distinct, nose tingling aroma. And much like plants that produce caffeine as a deterrent to bugs, wasabi uses this as a defence against pathogens.
Of course, I had to test this for myself.
I took a fresh bread roll, all natural and sourdough (to avoid preservatives and softening agents) and cut it in half. One half I dropped into a glass jar, covered the top with a layer of clingfilm (plastic wrap) and closed the lid over it. I repeated this for the other half, but included a sheet of greaseproof paper on top of the bread, with a small piece of wasabi paste in the middle. Thanks to the nature of sourdough, neither half did much for a while, then slowly, the half without any wasabi started to turn fuzzy. Over the following months it went from white fuzz to bluey green bloom, to black, all the while the bread grew smaller and smaller, collapsing upon itself as the mould gradually digested it from within.
Meanwhile, the wasabi half remained spotless.
Six months later, in the height of summer, I noticed a tiny patch of white mould had appeared on what would be the softer underside of the roll. Guessing that this was a combination of warm favourable conditions and a sign the wasabi had run out of juice, I removed the old paste and replaced it with fresh. A day later, all signs of mould had vanished.
Now, I’m not going to eat the bread, nor would I suggest you do it (afterall, it’s rock hard and dried out), but it presents interesting possibilities for solid fermentation like miso and cheese making. I’ve tested with all sorts of wasabi, both cheap and expensive, as well as horseradish and mustard and found that high quality wasabi and horseradish both perform best, with the latter requiring more frequent refreshing over the summer (every two months or so). As I write this newsletter, I share my desk with two halves of the bread roll. One of which is now an unrecognisable black mass of mummified starch, the other is still a pristine, albeit slightly dry looking piece of bread. Who knows how long it will last for?
Closing words
I appreciate that all koji related recipes are very niche, but I feel like miso makes for one of the easiest ways into the world of koji. I don’t plan to make a huge amount of what I share here as niche as this, but I’ve never been able to add quite so much information about the topic of miso in any one document, and I feel like Substack is the perfect place to share my most nerd fascinations. If you’re interested to learn more then let me know, but for now we’ll return to more casual recipes and fermentation.
Thank you for joining me, and I hope you have a great week.
Sam
Love the depth of detail here, Sam. Thanks very much for that. I think you've finally pushed me over the edge to make my own miso. I've been hovering since I read the Art of Fermentation but now I'm convinced.
Fascinating! So you can use any kind of pea or bean?