Simmer the kipper fillets in the bag as directed. When cool enough to handle, discard the skin from the fillets.
Mash or pound the kipper flesh along with the juices from the bag. Cream the butter until soft and beat in the kipper flesh.
Season to taste with just a little salt, plenty of pepper and a squeeze of lemon juice to sharpen the flavour. For a really smooth mixture combine the ingredients in a blender.
Spoon the pâté into a small serving dish, rough up the surface and chill for several hours. Garnish with a twist of lemon or a little chopped parsley and serve with hot toast.