SALMON A LA MORNAY

4 cooked potatoes
1/2 cup Swiss cheese
1 egg yolk
Buttered crumbs
1 cup medium white sauce
2 cups boiled salmon or 1 can salmon

Mash the potatoes and line a greased baking dish with them. Add the cheese and egg yolk to the white sauce and pour half of it over the potatoes. Add the fish and cover it with the remaining sauce and buttered bread crumbs. Bake in the oven for twenty minutes.