Heat oven to 350°F. Spray 2 1/2-quart casserole with cooking spray. Cook and drain macaroni as directed on package using minimum cook time. Rinse and return to saucepan.
While macaroni is cooking, in 3-quart saucepan, melt butter over medium heat. Cook and stir onion in butter 2 to 3 minutes or until softened. Stir in flour; cook and stir 1 minute. Gradually stir in half-and-half, mustard, pepper sauce and salt; heat until thickened and bubbly, stirring constantly, about 5 minutes. Stir in beer. Remove from heat; let stand 2 to 3 minutes. Stir in cheese until melted. Add sausages to cooked macaroni. Stir in cheese sauce. Spoon macaroni mixture into casserole.
Bake 30 to 40 minutes or until bubbly and top begins to brown. Top with popcorn just before serving.