1. Melt butter in a saucepan over medium-high heat. Add flour and cook for one minute whisking constantly. Slowly add milk, continuing to whisk. Add salt, nutmeg, and cayenne pepper. Cook for 2 to 3 minutes.
5. Spoon half the pasta mixture into prepared pan. Spread ½ cup mozzarella cheese evenly over. Layer the rest of the pasta mixture over the cheese then top with remaining mozzarella cheese. Top with panko mixture.