Crumble the sausage into a skillet. Cook over medium heat. Drain. Mix together cooked sausage, toast, cheese, mustard, salt, eggs, and milk. Pour into a greased, 9 x 13 inch baking dish. Cover. Refrigerate overnight. Bake, covered, at 350ºF.(175ºC.) for 45 to 60 minutes. Uncover, and reduce temperature to 325ºF.(165ºC). Bake for an additional 30 minutes, or until set.