the best we've ever had.
Sauté onions in butter until tender; stir in flour & seasonings & cook 1 min.
Add milk & cook, stirring constantly, until thickened. Remove from heat.
Add cheese, Worcestershire sauce & mustard. Stir until smooth.
Meanwhile, cook macaroni & add to sauce. Taste for seasoning.
Turn into buttered dish & sprinkle with remaining cheese.
Bake at 375 for 20 mins.
Note: if desired, can combine small amount of melted butter with breadcrumbs as a topping.