Boil a medium-sized 2-½ to 3 pound lobster and allow it to cool. When cold, split it in two and dice all of the meat. Heat 2 tablespoons butter and saute the lobster meat in it for several minutes. Add the sherry, the flour, and the cup of cream. Simmer gently for about 10 minutes, then add the beaten egg yolks mixed with 1 tablespoon melted butter and cream. Mix all thoroughly and fill the lobster shells. Bake in a hot oven until lightly browned, or while still hot run under the broiler.