(Using canned mushrooms)
Make a brown roux, using one tablespoonful of butter and the flour; add the stock and a half cupful of liquor from the can of mushrooms. Cook for five minutes, stirring all the time; then add the mushrooms, lemon-juice, salt and pepper. Let the mushrooms become well heated; then remove from the fire and stir in the yolk rubbed with a teaspoonful of butter. Stir the hot sauce until the egg is set; add the parsley and serve; or a half teaspoonful of kitchen bouquet may be used and the egg and parsley omitted.
This sauce may be served on the same dish with beefsteaks, fowls, etc., and the mushrooms laid evenly, top side up, around the meat as a garnish.
It may be made a white sauce by making a white roux, using white stock and leaving out the kitchen bouquet. The mushrooms are sometimes cut into halves or quarters.