What do you do with the skeletons of your small, oily fish? If you're like most people, you probably throw them in the compost. But if you're like Michael Ceraldi (of Ceraldi in Wellfleet), you put them in a bucket, layer them with salt, and leave them in the fridge to ferment.
What you're looking to make is garum. If this sounds like a stinky process, well, it is. But it used to be even stinkier. Garum is a fermented fish sauce that was wildly popular in Roman times, when it was made in factories by the sea. These factories produced it by leaving fish and salt in vats in the hot sun, leaving them to ferment. First the salt pulled the liquid out of the fish, then the liquid slowly settled into layers and was graded just like olive oil. Rich people bought the expensive top-notch stuff to marinate meats and serve with nice cheeses, and peasants bought the cheap stuff to flavor their porridges. Each port had its own recipe, and there were factories everywhere. They stank, so they were usually outside city walls.
(Fun garum trivia fact: In 2008, archaeologists found garum residue in Pompeii and used it to confirm the date of the eruption of Mount Vesuvius. The fish used were bogues, which come in the summer, so they were able to confirm that the volcano blew in August. Cool, huh?)
At any rate, for a while there, garum was as popular as ketchup is today. It was mixed with wine or vinegar, diluted with water and given to soldiers thanks to high protein and B vitamin counts, or mixed with honey to make a sweet condiment. Michael says he likes it best as a marinade for steak, or mixed with honey, thyme, mustard seed, and olive oil to make a sauce for fried chicken or pecorino cheese. It's different than most fish sauces I've had in that it's thin and oily—not thick and syrupy. The smell is similar, though—that intense fishiness that is somehow both terrible and wonderful, but mostly wonderful. A little goes a long way.
It's not a project for everyone, but it's a cool thing to know about. As Michael told me, he likes to know how to make everything from scratch. Because you never know when you might need to churn your own butter, or make your own bread, or bring back garum to the masses. Right?