Preheat oven to 350 degrees and lightly grease a 7X11-inch baking dish.
Melt butter in a large saucepan over medium heat.
Sprinkle in flour and whisk in, cooking for 1 minute.
Gradually whisk in milk and half-and-half. Keep whisking until it comes to a simmer and simmer for about 2 minutes.
Add cayenne pepper, salt and black pepper.
Turn heat to low. Add cheese a handful at a time, whisking until melted.
Add cooked pasta to prepared pan. Pour cheese sauce on top, stirring to mix the cheese sauce in.
Combine crushed cheetos and melted butter and scatter evenly on top.
Bake for 15 to 20 minutes.