Cut the bread in slices of one inch in thickness.
Stamp into rounds with a circular pastry-cutter; scoop out the inside, making little nests of them.
Fry in hot fat (see French Frying); drain them on kitchen paper.
Put them inside the oven to keep hot.
Put the butter and water into a saucepan on the fire to boil.
When boiling, stir in sufficient crumbs to make the mixture stiff.
Beat in the yolk, add pepper, salt, and cayenne; and stir in the cheese.
Pile the mixture on the cases; sprinkle a few browned crumbs over them and be careful to serve quite hot.