Pan-frying fish with the skin on

Why

Fish skin is a thin layer of collagen with fat beneath it; in a hot pan the water must first evaporate from it, then the fat renders and the skin dries, browns and crisps. As long as the skin is wet, the water holds it at around 100 °C, the proteins grip the metal and the skin stays in the pan when you try to turn it; once it crisps and browns it usually releases by itself, much like searing meat (see the Searing meat card). Collagen also shrinks in the heat, so the fillet bows, the skin lifts away from the pan in the middle and stays rubbery; shallow scoring of the skin and briefly pressing the fillet with a spatula help. Fish is done much sooner than the meat of land animals, so the fillet cooks mainly on the skin side, which protects it, and only finishes briefly on the other side (see the Fish: when is it done card).

How to do it

• Pat the fillet dry with paper towel and scrape the skin from tail to head with the back of a knife; this pushes out water and any remaining scales.
• Score the skin with 3–4 shallow cuts through the skin only, not the flesh; salt the fish just before cooking, or salt the flesh side at least 45 minutes ahead and keep it in the fridge.
• Heat the pan with a thin layer of oil that tolerates high heat; do not heat an empty non-stick pan on full.
• Lay the fillet skin side down, away from you, and press it with a spatula for 20–30 seconds so the whole skin makes contact.
• Then turn the heat straight down to medium-low and do not move the fillet until the skin has browned and the flesh has turned opaque about three quarters of the way up.
• Turn it only when the skin releases by itself, finish the other side briefly to 63 °C in the centre and serve skin side up so it stays crisp.

If it goes wrong

If the skin sticks, do not prise it off: let the fillet cook for another minute or two, the skin often releases by itself once it crisps. Peel off torn skin, crisp it separately in the pan and serve it on top. Crisp rubbery skin in the pan skin side down without turning; if the flesh is already done, remove the skin and serve the fish without it, with a sauce.