Melt the beef drippings in a heavy saucepan. Add the Mirepoix. When this begins to color, add the flour and stir until the flour is thoroughly browned. Add the peppercorns, tomatoes and parsley. Mix well and add the beef stock. Simmer 2 1/2 hours or it has been reduced by 1/2. Stir occasionally and skim off the fat as it rises. Strain and stir occasionally as the sauce cools to prevent it from forming a skin. The finished sauce should be about the consistency of whipping cream.