Wash the shells and put them in hot water to open them. Take out the fish, and put them in a saucepan on the fire with a little water; chop two onions small and fry them in butter; while stirring them about dredge in slowly a little flour; add the oysters and Tapes, and the water in which they were boiled, stir the whole for a few minutes over the fire, then add the yolk of an egg well beaten up. Fry slices of bread in butter, and place them at the bottom of the dish, pouring the potage over them; then serve.
Wash the shells, then boil them for a few minutes, till the water is just on the eve of boiling over. If boiled with cockles, the " butterfish" must be placed in the saucepan a few seconds before the cockles. They are also very good eaten raw, like oysters.