Cook two tablespoons butter with one sliced onion five minutes. Add one and one-half cups mushroom caps finely chopped, and one small parboiled sweetbread, finely chopped; then add one cup White Sauce II, one-fourth cup stale bread crumbs, one red pepper chopped, one-half teaspoon salt, yolks two eggs, well beaten, and whites two eggs, beaten until stiff. Fill buttered timbale moulds, set in pan of hot water, cover with buttered paper, and bake fifteen minutes. Remove to serving dish and pour around
Mushroom Sauce. Clean five large mushroom caps, cut in halves crosswise, then in slices. Sauté in three tablespoons butter five minutes; dredge with two tablespoons flour, add one-third cup cream and one cup chicken stock, and cook two minutes. Season with salt and paprika, and add one chopped truffle.