Bacalhau — dried, salted cod — is the foundation of Portuguese cuisine with reportedly over 1,000 recipes. The preparation technique is the critical first step: proper desalting (dessalgue) takes 24-48 hours of soaking in cold water with regular water changes. Under-soaked cod is inedibly salty; over-soaked cod loses its distinctive flavour and becomes bland fresh fish. The transformation from stiff, salt-encrusted board to tender, flavourful protein is a technique in itself. After desalting, the cod can be baked, grilled, fried, shredded, or braised — each of Portugal's regional preparations builds on this common starting point.
Soak salt cod in cold water for 24-48 hours in the refrigerator (never at room temperature). Change the water every 6-8 hours — each change removes more salt. Thicker pieces need longer soaking than thin fillets. Test by tasting a small piece after 24 hours — it should be pleasantly seasoned, not aggressively salty. The cod is never truly 'unsalted' — a background saltiness is the point. After soaking, the cod is often briefly poached in simmering (not boiling) water for 2-3 minutes to soften the flesh before the main preparation. Reserve the poaching water — it contains flavour and can be used to cook potatoes.
For Bacalhau à Brás: shred the desalted cod finely, fry with matchstick potatoes, fold in scrambled eggs, finish with olives and parsley. For Bacalhau à Gomes de Sá: layer with sliced potatoes, onions, garlic, olive oil, hard-boiled eggs. The cataplana (clamshell copper pot from the Algarve) is Portugal's signature cooking vessel — its sealed dome creates a self-basting steam environment perfect for seafood. A Dutch oven with a tight lid is the closest substitute.
Not soaking long enough — this is the most common error and ruins the dish. Soaking at room temperature — bacteria risk. Not changing the water regularly. Boiling the cod aggressively — it should be gently poached. Treating desalted bacalhau like fresh cod — it has different texture and moisture content. Over-soaking until all salt is gone — you want some residual seasoning.