Bacon and Caramelized Onion Mac 'n Cheese

Directions

1. 1Spray 12-inch nonstick skillet with cooking spray; heat over medium heat. Add onions to skillet; cook uncovered 10 minutes, stirring every 3 to 4 minutes, until tender and starting to brown. Reduce heat to medium-low. Cook 35 to 40 minutes longer, stirring every 5 minutes, until onions are deep golden brown; set aside.
2. 2Meanwhile, cook and drain pasta as directed on package except omit salt. Spray 11x7-inch (2-quart) baking dish with cooking spray. Pour pasta into baking dish; keep warm.
3. 3While pasta is cooking, make cheese sauce. In 3-quart saucepan, melt butter over medium heat. Stir in flour, salt, pepper and mustard with wire whisk. Cook about 2 minutes, stirring constantly, until mixture is smooth and bubbly; remove from heat. Gradually stir in milk. Heat to boiling, stirring constantly; boil and stir 1 minute. Remove from heat; stir in caramelized onions and all remaining cheese sauce ingredients.
4. 4Heat oven to 400°F. Pour cheese sauce over pasta in baking dish. Sprinkle with topping ingredients. Bake uncovered 10 minutes or until heated through (topping will not be brown).