Classic Southern Macaroni and Cheese Bake

6 tablespoons butter, divided
1/4 cup flour
1 teaspoon salt
1/2 teaspoon dry mustard
1/4 teaspoon pepper
3/4 teaspoon Worcestershire
3 cups milk
1 small onion, grated
3 cups shredded sharp Cheddar cheese
8 ounces elbow macaroni, cooked and drained
3/4 cup soft bread crumbs

Directions:
In saucepan over medium low heat melt 4 tablespoons butter; blend in flour and seasonings, stirring until smooth and bubbly. Gradually sitr in milk; cook and stir until thick and smooth Stirin grated onion and cheese. Place cooked drained macaroni in a buttered 3-quart casserole. Poutr sauce over macaroni and gently mix to blend. Melt remaining tablespoons of butter and toss with the bread crumbs. Sprinkle bread crumbs over the macaroni. Bake at 375 degrees for 30 minutes, or until golden brown. Serves 4-6.