The fermentation room beneath Hudson Street

Down a set of iron stairs behind the Tribeca dish pit there is a room that was a cold store for a textile business in the 1940s. Twelve feet by nine, brick on three sides, and it sits at twelve degrees Celsius all year without any help from us because it is below the water table and surrounded by the foundations of the building. When we took the lease in 2015 it was full of broken pallets. In 2018 we cleared it out, whitewashed the brick, put in stainless shelving and a hand sink, and started using it properly. It is the least photogenic room in the company and the most useful.

Right now there are about four hundred litres of things in there, in glass and in food grade HDPE, all of it labelled with what it is, who started it, the date and the target pH. I want to describe what is actually down there, because fermentation has become the sort of word restaurants put on a website without owning any of it, and also because the honest version includes throwing things away.

What lives down there

Koji first, because most of the rest depends on it. We grow Aspergillus oryzae on pearl barley in a converted proofing box at thirty degrees, and it takes about forty two hours to go from inoculated grain to a solid white block that smells of chestnut and pineapple. We make roughly eight kilos a week. Some of it is used fresh, blitzed into the koji butter that goes on the black garlic madeleine. Most of it becomes something else.

Garum is the biggest single volume. Ours are protein sauces made by breaking down meat trim with koji and thirty percent salt at fifty five degrees for eight to ten weeks. There are three crocks going at any time: duck, from the wing tips and skin that Isolde's aging cabinet produces, beef, from tartare trim, and one from the leek and allium ends the garde manger would otherwise compost. They finish somewhere between soy sauce and a very good stock, and about a teaspoon of the duck one goes into the jus for the aged duck course.

Then vinegars, which are the most straightforward and the slowest. Wine that did not sell by the glass goes into three ten litre carboys with a mother, and eleven weeks later it is vinegar with a house character we could not buy. We make around sixty litres a year and it costs us essentially nothing except the shelf space.

Black garlic sits in a cabinet in the corner at sixty degrees and eighty percent humidity for ninety days. That is not fermentation at all, strictly speaking. It is the Maillard reaction running very slowly, so calling it fermented is wrong and I have stopped doing it. It is also the product we sell most of in the Pantry, so a lot of people now have a jar of our slowly browned garlic in their kitchen under a slightly inaccurate name.

And then the small things: sour cherries in brine for the duck course, pickled green walnuts started every June for the following winter, a lactic ferment of whatever brassica the farm oversupplies, and a pear vinegar shrub that Delphine takes upstairs for the zero proof list.

How we keep it safe

Everything in that room is controlled by one of three barriers, and every jar is labelled with which one applies to it. Salt, for the garums, at thirty percent of the weight of the trim, which is high enough that nothing dangerous can establish itself even at fifty five degrees. Acid, for the lactic ferments and vinegars, held below pH 4.2 and checked with a calibrated meter rather than paper strips. And low water activity for the dried and cured items.

We calibrate the pH meter every Monday against two buffer solutions and write the reading in the same book we use for the aging cabinet. Anything that has not reached its target pH within the expected window is destroyed rather than nursed along. The whole programme is documented in a variance filed with the New York City Department of Health, which is the piece most home fermentation writing leaves out: if you are selling it to the public in this city, you need paperwork, and getting it is not difficult but it is not optional.

We do not make anything anaerobic in a sealed low acid container, which rules out several things I would personally like to try, because the risk from Clostridium botulinum is not worth one interesting course.

The two we threw away

In April an allium garum went wrong in a way I still cannot fully explain. It was at thirty percent salt and fifty five degrees like the others, but at week five it started smelling of solvent and its pH had drifted up rather than down. Twenty two litres in the bin. My best guess is contaminated leek ends, harvested from a delivery that had sat too long in the walk in before anyone got to it.

In September a brassica ferment developed a pink film on the surface. Not kahm yeast, which is white and harmless and gets skimmed. Something pink, which is not on the list of things I am willing to identify by eye. Eight litres gone.

Both were entirely avoidable and both came from the same root cause, which is that the person who started the batch was not the person who checked it on day four. We changed the rota after the second one so a single cook owns a batch from start to finish. There has not been a failure since.

Why bother

Partly because it makes the food taste like this restaurant and not like a restaurant. You cannot buy our duck garum, so the jus on that course is not reproducible anywhere else, and that is worth more to us than any technique we could copy from a book.

Mostly, though, it is because of what it does to waste. In 2025 that room absorbed roughly one and a half tons of trim, ends, bones and skin that would otherwise have been composted at best. Composting is fine. Turning it into the thing you season the next dish with is better, and it is the closest thing to a free ingredient a kitchen ever gets.