You don't even have to grate cheese for this tempting mac and cheese.
Preheat oven to 375 degrees.
In 3-quart saucepan cook onions in 2 tablespoons of butter over medium heat for 3 minutes. Stir in mustard. Add cheese, milk and pepper. Cook and stir until cheese is melted and mixture is smooth. Stir in macaroni, spoon half into buttered 2 to 3-quart casserole. Cover with broccoli, then top with remaining macaroni mixture.
Melt the remaining butter toss with cracker crumbs in small bowl. Sprinkle crumbs over casserole. Bake for 25-30 minutes until bubbly and browned. Let stand for 10 minutes before serving.
Cooks note: After the pasta is done cooking remove with a slotted spoon to a colander and use the same water to boil the broccoli.