Fry onion in butter with some bits of cut-up ham, then pour Marsala over it, and blond of veal, add thyme, bay leaf, peppercorns, clove, mushroom cuttings, and reduce half.
In another saucepan put Espagnole sauce, tomato sauce, and game stock or essence. Reduce a third, and add the contents of the first saucepan, boil the sauce a few minutes, and pass it through a sieve. Warm it up in a bain-marie before using.