Whole Grilled Mackerel, Herring or Trout in Oatmeal

Cook’s Tip: For a special occasion a hard butter can be made with 125g (4oz) softened butter mixed with two teaspoons lemon juice, one tablespoon chopped parsley and three tablespoons Drambuie. Wrapped in clingfilm and foil and shaped into a cylinder, it should be left to harden in the fridge before cutting and slicing on top of the fried fish. It can be cut into slices and deep frozen.