How to turn veg scraps into an ancient seasoning – recipe | Food

TToday’s recipe is the pinnacle of zero-waste cooking. If all else fails and you have a compost bin full of veggie scraps, they can still be saved by turning them into garum, an ancient Roman sauce traditionally made with fermented fish and more recently other meat, plant products, and even peels. It is similar to Worcestershire sauce, fish sauce, and soy sauce and is used in the same way for flavoring and incredible depth of flavor.

Garum has been repopulated and reinvented in recent years by fermentation experts like Sandor Katz and Noma’s fermentation lab. Experimentation has resulted in all types of garums made with animal products and vegetables alike, using everything from eel and emu to coffee waste and compost. When I spoke to Katz about making my own, he suggested being selective with my scraps to create a more distinctive, better-tasting end product — celeriac and onion-skin garum, say, or leek tip garum.

My recipe is adapted from one in Katz’s latest book, Fermentation Journeys. It was developed by Patrick Marxer, a food waste pioneer in Zurich, who makes garums from restaurant waste and sends them back to cook.

Veg-scrap garum (aka compost sauce)

Garum is an umami flavor bomb that has been used in cooking for centuries. It was particularly popular in ancient Roman cooking and was used in everything from lamb stews to salad dressings. Admittedly, fermenting your own garum is an affair of the heart, not least because of the time it takes. I suggest storing leftover veggies in the freezer until you have enough to make this high volume recipe. Use it like soy sauce to add salt and umami to any dish.

As Katz writes in his book, Marxer incubates his garum at 60 °C (140 °F) to protect it from bacterial development, but Katz suggests fermenting at a lower temperature is an “improvement.” Processing at a higher temperature speeds up the process, while slow fermentation, as garum was traditionally made, can result in a deeper flavor. To protect the sauce from harmful bacteria, Katz suggests using a higher salt percentage of 6%; Noma, meanwhile, suggests a higher salt percentage of 18%, so I’ve settled on a safe middle ground here of around 10%. Katz also recommends stirring the garum daily, at least initially, to prevent mold from forming on the top; After about a month, when the main active part of the fermentation process is over, stir less often, maybe once a week. I made mine using two types of juice pulp scraps donated to me by a local juice bar. The juicer perfectly chops the vegetables, ready for making garum.

500 g leftover vegetables (e.g. onion skins, vegetable skins, used coffee grounds)
300 grams of koji – get this fermented rice or soybean mix at Asian supermarkets, health food stores, and online
160 grams of sea salt

Chop or pulse the leftover veggies until finely chopped. In a large, clean pot or bucket, combine koji and sea salt, then cover with 800ml of cold water. Decant into Kilner jars or similar with the lid on but not closed to allow any gases to escape. Store out of direct sunlight in a low cupboard where the temperature is relatively stable for at least eight or nine months and ideally a year. Stir daily at the beginning of the fermentation process to avoid mold growth on the surface, then less regularly when fermentation stabilizes. When the garum is at its best, store in clean bottles or jars, seal and use within two years.