1To make the fish stock, rinse and clean: 3 pounds fish bones and heads (gills removed), white-fleshed fish only.
2If necessary, chop the bones so they will fit in a large heavy pot. Prepare: 1 onion, peeled and sliced, 1 small carrot, peeled and sliced, 1 small fennel bulb, trimmed and sliced, 3 medium tomatoes, cored and coarsely chopped, 1 head of garlic, cut in half horizontally.