Preheat oven to 350 degrees. Grease an 8X8X2 inches glass baking dish. Cook macaroni in medium pot of boiling salted water until just tender but still firm to bite, stirring occasionally. Drain macaroni and place in large bowl. Add butter and toss until melted. Mix in 2 cups cheddar cheese. Beat milk, eggs, mustard, Worcestershire sauce and cayenne pepper in medium bowl to blend. Stir egg mixture into macaroni. Transfer to prepared dish; sprinkle remaining 1/2 cup cheddar cheese over top.
Bake macaroni until golden on top and set in center, about 1 hours.