Fish pie is Britain’s great fish bake — pieces of fish folded through a white sauce under a blanket of mashed potato — Britain’s great fish bake. Chunks of cod, haddock, salmon, and smoked fish are folded through a parsley, cheese, or mustard sauce, sometimes with prawns and hard-boiled eggs, then capped with mashed potato — piped, forked, or rough — and baked until golden and bubbling. It is the sea’s answer to shepherd’s pie: the catch stretched with sauce and potato into a family meal. The sauce keeps the fish moist, the potato crisps on top, and the whole thing feeds a crowd from modest ingredients. Variations are endless, but the formula holds — fish, sauce, mash, oven — one of the most forgiving and most loved bakes in the repertoire.