In a large kettle, bring 3 or more quarts of water to a boil. Add 3 tsp. salt and slowly the macaroni, bring back to a boil, cook 7 to 9 minutes, uncovered with water rapidly boiling.Drain & rinse.

Mince the onion. Put it in the top of a double boiler with the butter. When butter is melted, stir in flour, mustard, salt and pepper. Slowly stir in milk. Cook until smooth and hot, stirring often. Add the mushroom soup. Stir until heated. Add grated cheese and stir until melted.

When macaroni is tender, drain in a colander, rinse and drain again. Turn into a greased 2 or3 quart casserole. Pour cheese sauce over macaroni, tossing lightly with a fork so all gets coated nicely.

Meanwhile, toss bread crumbs in 3 tbsp. butter melted in a fry pan. Stir until blended and slightly browned and set aside. Just before cooking, sprinkle casserole with bread crumbs. Bake, uncovered, 20 minutes at 400 F or 35 minutes at 350 F. Makes 6 servings.

NOTE: For 3 people, prepare as directed, but put into 2 small buttered casseroles,(without bread crumbs). Cover with aluminum foil and freeze. Thaw at least 4 hours at room temp.Cover with crumbs, bake at 350F for 25 - 35 minutes.