Bouillabaisse

Use a mix of firm, flavourful fish; traditional versions use Mediterranean rockfish, while sea bass, monkfish or gurnard work well when those are unavailable. Add delicate fillets near the end so they hold together.

Make the aromatic broth first, then simmer the fish gently in it rather than boiling hard. Add thick, firm pieces first and delicate fillets last; they usually need only a few minutes, until opaque and just flaking.

Serve the broth with toasted bread spread with rouille, a garlicky sauce often coloured with saffron or chilli. The fish can be served separately, or in the bowls with the broth.

Make the broth ahead, chill it promptly and keep it covered in the fridge; reheat it until steaming before adding the fish. Cooking the fish only when you are ready to serve helps it stay tender.

The broth freezes well on its own. Fish can become dry or break up after freezing and reheating, so freeze the broth and add fresh fish when you serve it.

Bouillabaisse is a Provençal fish stew associated with Marseille, traditionally made with several kinds of fish and a strongly flavoured broth with ingredients such as fennel and saffron. Recipes for fish soup are broader and need not use that mix or style.

Yes: thaw it safely in the fridge and pat it dry before adding it, so excess water does not dilute the broth. Add it gently and avoid stirring once the pieces are cooking.

Cool leftovers promptly, transfer them to a covered container and refrigerate within two hours; eat within two days and reheat only once until steaming throughout. If the fish has been sitting out longer, discard it.