Many of us buy fish already filleted or ask our fishmongers to do it, but by buying the whole fish, we can get a lot more out of it. Very little of a fish needs to be thrown out, and if you’re familiar with their anatomy, many parts that are usually discarded can be used and are often delicious.
For example, the heads of large fish (monkfish, dentex, grouper, amberjack, skate, etc.), which are usually thrown away, are in fact full of bits of meat that can be used for soups, ragùs and more. Scraps left over from filleting, rich in fine fat, can be used to make pâtés, terrines or stuffings.
The head, bones, fins and unscaled skin (though not the guts and gills, which must be thrown out) can also be used to make fumet, a reduced fish stock with many uses in the kitchen. Fumet can be used in fish braises, in broths for risotto, as a base for sauces or to flavor soups, and has different characteristics depending on the type of fish used. For example, scorpion fish, mullet, weevers, tub gurnard, monkfish and other fish used in soups make a strongly flavored, complex fumet. For a subtler, more elegant fumet, use sole and turbot, or for even greater delicacy, bass or bream. Not all fish can be used for fumet; oily fish like anchovies, sardines and mackerel, for example, are not suitable.
Fumet is simple to make and does not take more than 45 minutes. After washing the bones, head and skin of the fish, put them in a saucepan where chopped onion, leek and carrot have already been sweated in oil or butter. Add a few peppercorns, a bouquet garni (parsley stalks, basil, thyme, bay) and, if you like, a few fresh or dried mushrooms. Add enough water to cover with water, simmer for 45 minutes and strain. The fumet can be stored in the refrigerator for a few days. We recommend making it when you have the fish available and then storing it in the freezer in small containers, or freezing it in ice-cube trays for easy portioning.
Extract from the book Scuola di cucina, Slow Food Editore.