A fish course covering pan-frying for crispy skin, en papillote steaming, curing and ceviche, and handling whole fish (scaling, filleting, roasting).
Cured and raw fish preparations rely on two transformations: 1. **Salt curing** denatures the proteins like heat does, but slower and without coagulating the moisture out. Texture firms up; flavour intensifies; the fish becomes safe to eat without further cooking (within reason; see below). 2. **Acid curing** (citrus juice, vinegar) does the same thing in 15-30 minutes. Looks "cooked" (opaque), but is technically still raw; the acid has folded the proteins.
En papillote ("in paper") is a French technique with Italian, North African and East Asian variants. Fish or seafood is placed on a sheet of parchment with vegetables, herbs, a flavoured liquid (wine, citrus juice, stock), and sealed inside the paper. The package goes into a hot oven. Steam from the fish and liquid cooks everything together; the paper traps the aromas.
Fish has half the connective tissue of meat. The proteins coagulate and the moisture evaporates at lower temperatures and faster than meat. Most home cooks treat fish like a smaller piece of chicken: cook it 8-10 minutes, season heavily, slap a sauce on it. The result is dry, dense, often grey.
Pan-frying is the workhorse technique for filleted fish. Done well, you get a sheet of crackling crisp skin, golden brown, with moist flaky flesh underneath that takes a sauce or salsa beautifully. Done badly, you get rubbery soggy skin (or skin stuck to the pan), and overcooked dry flesh.
A whole fish is dramatically better value than a filleted one. The fishmonger charges by the whole-fish weight; you get the fillets, the head, the bones, the cheeks. The "fillet yield" is about 50% - half the fish is meat - but the rest is the foundation for fish stock, the cook's reward (cheeks, eaten standing up at the counter), and the head for sauce or display.