Recipes from Noma’s food lab that you can recreate at home in a Kilner jar.

From kombucha to kimchi, fermented foods are everywhere right now. The trend is thanks in part to Mr René Redzepi, chef and co-owner of Noma, the coveted Copenhagen restaurant that’s a near-permanent fixture on the World’s 50 Best list. If you’ve seen foraged sea herbs or wild game on a menu lately, there’s a chance it’s down to Mr Redzepi, who has pioneered the use of hyper-seasonal, hyper-local ingredients inspired by the rugged Scandinavian landscape surrounding his restaurant. As dictated by traditional Scandinavian cooking, the Noma team need ways to stock their pantry shelves during the cold Nordic winters, when fresh produce is less abundant. And that’s where fermenting comes in. Noma’s kitchen now includes a purpose-built fermentation lab, where a treasure-trove of vinegars, kombuchas, misos and more in varying states of maturity line the shelves. The results of these experiments, from hazelnut miso to lacto-fermented blueberries, bring an unrivalled depth of flavour to Noma’s dishes.

Now, Mr Redzepi – along with co-author (and head of the fermentation lab) Mr David Zilber – is helping home cooks try Noma’s techniques in their own kitchens. Their book, The Noma Guide To Fermentation, includes chapters on eight fermented foods, with step-by-step guides and recipe ideas. “It’s exhilarating to think that people will get a sense of how we cook at Noma,” writes Mr Redzepi.

Fermentation is a broad term and can be applied to foods from beer and cheese to kimchi and soy sauce. “They’re all dramatically different creations,” writes Mr Redzepi, “but they’re unified by the same process. Microbes break down or convert the molecules in food, producing new flavours as a result.” Fermented foods share an umami-rich, complex profile that enhances the taste of other ingredients.

One of the key techniques outlined in the book is lacto-fermenting. “There’s not a dish on the menu at Noma which doesn’t involve some element of lactic acid fermentation,” writes Mr Redzepi. Fermented wild mushrooms, for example, are made into a syrup that’s paired with chocolate. “Just a drop of it will make your tongue stand up,” writes Mr Redzepi. Lacto-fermenting is a deceptively simple process. “Weigh your ingredient, add 2 per cent salt by weight, then wait.” The longer you leave the fruit or vegetable – be it plums, gooseberries or white asparagus – the sourer the resulting taste will be.

Once you’ve mastered fermented fruit, it’s time to try kombucha.  “Ten years ago, hardly anyone in Denmark was drinking kombucha,” writes Mr Redzepi. These days, the lightly sparkling, fermented drink, said to originate in China around 200 BC, is widely praised for its healthy gut-maintaining properties, and can be found on modish cocktail menus and supermarket shelves. It’s made by fermenting sweet tea or fruit juice. When the sugar turns first to alcohol, then acetic acid, it creates a sweet-but-sour drink. The chefs at Noma use a coffee kombucha in tiramisu, while a lemon verbena version is added to vinaigrettes.

Vinegar, that kitchen staple, is another product which has fermentation to thank for its flavour-enhancing powers. “Throughout Europe, a splash of vinegar is a way to inject freshness into whatever you’re cooking,” writes Mr Redzepi. Like kombucha, vinegar is made when yeast and bacteria combine. When the yeasts die off, the vinegar plateaus at a level of acidity and can be aged to allow the flavour to intensify. Forget the fish and chip shop stuff: Noma’s array of vinegars include butternut squash, honey or sweet pear.

The book also explores some lesser-known forms of fermentation. There’s koji – a Japanese term to describe a mould which grows on cooked grains – and miso, a fermented paste made from cooked soybeans, koji and salt. The truly adventurous home fermenter can try their hand at garum, a seasoning usually made from fish, salt and water.

Like microbes multiplying in a Kilner jar, our appetite and sense of adventure for fermented food only looks set to grow. Try the trend yourself with one of Mr Redzepi’s recipes, below, and impress guests by cooking like a top Scandi chef.

“The true prize of this recipe is the fermented juice that leaches out of the ceps (aka porcinis), Mr Redzepi writes. “It’s like a Swiss Army knife for us in the Noma kitchen – we use it to season everything from fennel tea to monkfish liver. It has a balance and funk that really electrify anything it touches. Makes 1kg lacto mushrooms and juice.”

1kg cleaned cep (porcini) mushrooms, frozen for at least 24 hours 20g non-iodized salt

Place the frozen mushrooms and salt in the vacuum bag and toss to mix thoroughly. Arrange the mushrooms in a single layer, then seal the bag on maximum suction. Be sure to seal the bag as close to the opening as possible, leaving headroom that will allow you to cut open the bag to vent any gas that accumulates and then reseal it.

Ferment the mushrooms in a warm place until they have released much of their liquid, yellowed slightly, and soured nicely. This should take 5 to 6 days at 28°C/82°F, or a few days longer at room temperature, but you should start taste-testing after the first few days.

Once the mushrooms have reached your desired level of sourness and earthiness, carefully remove them from the bag or fermentation vessel. Strain the juice through a fine-mesh sieve. The mushrooms and their juice can be stored in separate containers in the refrigerator for a few days without a noticeable change in flavour. To prevent further fermentation, you can also freeze the mushrooms individually on a tray, transfer them to vacuum-sealed bags or zip-top freezer bags with the air removed, and keep in the freezer.

The Noma Guide To Fermentation (Artisan) by Messrs René Redzepi and David Zilber is out now