Bavaroise Sauce

Reduce to half its volume one gill of vinegar; take it from the fire and let get cold, then add one gill of bechamel (No. 409), four raw egg-yolks and four ounces of butter divided into small pats, a gill of water, salt and nutmeg. Stir the preparation over a moderate fire until it thickens, then incorporate into it three ounces of butter, a small bit at a time, working it in well with a whip so as to have it light, add to finish, three ounces of crawfish butter (No. 573) and a tablespoonful of grated horseradish.