Cook 4 slices bacon till crisp. Remove bacon, reserving about 3 Tbsp drippings in skillet. Drain and crumble bacon; set aside. Cook 1/2 cup chopped onion in reserved drippings till tender. Stir in two 16-ounce cans pork and beans in tomato sauce, 2 Tbsp brown sugar, 2 Tbsp catsup, 1 Tbsp Worcestershire sauce, and 1 Tbsp prepared mustard. Turn into a 1 1/2 quart casserole. Bake, uncovered, in a 350 degree oven for 1 1/2 to 1 3/4 hours, or cook in the microwave oven on Hi for 10 to 12 minutes. Stir 1/2 way through cooking time, Top with bacon. Let stand a few minutes before serving.