Cook pasta according to package directions; drain., Meanwhile, in a large cast-iron or other heavy skillet, melt butter over medium heat. Stir in flour until smooth; gradually whisk in cream. Bring to a boil, stirring constantly. Cook and stir until thickened, about 2 minutes. Reduce heat; stir in cheese until melted., Add macaroni; cook and stir until heated through. Top as desired.