Cook macaroni according to package directions; drain and set aside.
In a large saucepan, melt butter. Stir in the flour, salt, mustard, pepper and Worcestershire sauce until smooth. Gradually add milk and cream. Bring to a boil. Cook and stir for 1 minute or until thickened. Stir in cheeses until melted. Stir macaroni into cheese mixture.
Transfer to a greased 2 quart baking dish. Sprinkle with bread crumbs, bacon, Parmesan cheese and onions. Bake uncovered at 350º for 20-25 minutes or until bubbly and golden brown.