Preheat the oven to 350 degrees. Spray a 9 X 13 " baking dish with cooking spray.

Bring a large pot of salted water to boil and cook the pasta according to manufacturer's instructions. When pasta is done, drain in a colander and then transfer to a large bowl. Stir in butter to coat the hot pasta.

Grate cheese in your food processor while pasta is cooking.

Blend the milk, eggs, mustard, Worcestershire and cayenne together.

Reserve 1 cup of grated cheese and stir the remaining grated cheese into the hot pasta, Then add the milk mixture and stir well. Pour into your baking dish.

Sprinkle reserved cheese evenly over casserole, then sprinkle panko evenly over the casserole.

Bake at 350 degrees about 40 minutes till cheese is melted and mixture is hot through.

If freezing, seal the casserole once assembled and freeze. Heat uncovered from frozen. Check for doneness after 60 minutes. It may take 75 minutes depending on the depth of your casserole dish.