Make two slits in each filet,about 3" long and not quite to the underside.Stuff these with slices of mushroom,bacon pieces and salt and pepper.Make marinade in a 9 x 9 x 3" pan or dish by combining the peppercorns,bay leaves,allspice,cloves,brandy, burgundy and vegetable oil.Place prepared filets in this mixture and refrigerate for 24 hours or more. Remove and drain filets,when ready to cook.Grill according to taste,rare,medium or well done.To make a sauce to cover meat,melt the 1/2 cup butter in a small saucepan.Stir in flour and brown. Blend in until smooth,the beef stock and 1 cup of marinade.Stir in mushrooms and heat through.Pour sauce over filets.Serves 4.Decorate with parsley and onion rings. Recipe is from Brennans Restaurant in New Orleans.