This is Ronzoni’s macaroni & cheese, but since it is not on their website it may be a bit dated.
1 pound elbow noodles or small shells, uncooked
1/2 cup butter
1 onion, diced
1/2 cup flour
2 tsp. dry ground mustard
1 1/2 tsp. salt
5 cups milk
4 cups shredded cheddar (or 2 cups cheddar and about 5 slices of american)
Cook pasta. Drain.
While the pasta is cooking, saute onion gently in butter until softened and clear, do not brown. Add flour, mustard and salt and stir well. Gradually add milk and cook until thickened and bubbly. Remove from heat and stir in half the cheese.
Stir sauce into pasta and pour into greased baking dish – 13 x 9. Top with remaining cheese.
Bake at 375˚ for 30-40 minutes until bubbly. Let stand 10 minutes. Makes 8-10 servings.