Preheat oven to 350 degrees. Grease a 9x13 baking dish.
In a large bowl, combine the cooked pasta, 2 cups of the cheddar cheese and all of the pepper jack cheese. Stir to combine. Pour into the prepared baking dish.
In a medium bowl, add the flour, salt, black pepper, cayenne pepper, mustard, sour cream, egg, milk and half & half. Whisk together to fully combine. Pour the mixture over the cheese and pasta.
Cover with the remaining 2 cups of cheddar cheese.
Bake uncovered for 45 minutes or until the top is beginning to brown.
Enjoy!