The recipe There are few moments in the kitchen I enjoy more than cooking a simple, perfect piece of fish. A simple thing, but when done with care will outshine any complicated affair. You need a shallow pan that doesn’t stick, some neatly trimmed fillets of fish, some butter, a few fine breadcrumbs and, if you like, some finely chopped herbs with which to season the crumbs. Check 4 large fillets of fish carefully for fine bones and remove them with tweezers. Finely chop 4 tbsp of fresh herbs – parley and dill or tarragon – and mix with 6 tbsp of fine, fresh, white breadcrumbs. Finely grate the zest of 2 limes and add it to the herbs and crumbs. Scatter the crumbs on a large plate. Press the fillets of fish down and press firmly into the crumbs so they stick to the fish. Turn the fish over and press to coat the other side. Melt 30g of butter in a shallow pan over a moderate heat, add 1 tbsp of olive oil and when bubbles appear around the edge, carefully lower in 2 of the fillets of fish, and let them cook for 5 or 6 minutes, spooning the lightly bubbling butter over them as they cook. Carefully check the underside – if the crumbs are golden then turn with a palette knife or fish slice and cook the other side. The fish is done when the crumbs are gold and the flesh is clean, bright white in colour. It should be firm to the touch. Serves 2 Lift the fillets from the pan and keep warm while you cook the remaining 2. Cod, bream, plaice or haddock is suitable here. Check that your fish is sustainably sourced. The thinner the fillet, the less time it will take to cook, so start checking at 4 or 5 minutes before turning. Try not to overcrowd the pan, it makes the fish difficult to turn. Better to cook each serving separately. The Observer aims to publish recipes for fish rated as sustainable by the Marine Conservation Society’s Good Fish Guide