Lightly butter a medium baking dish with 1 tablespoon butter. Season haddock fillets with salt and pepper. In a small bowl mix together egg yolk and mustard. Brush this mixture liberally over top ...

Cover the haddock fillets with the rock salt and refrigerate for 10 minutes, then rinse the salt off under cold running water and pat the fish dry with kitchen paper. Set aside. Preheat the oven ...