Set your oven to 350°F degrees and generously grease a 9x13 baking dish with food spray.
Cook the pasta according to package instructions.
In the meantime, prepare the roux by combining flour and butter in a pan. Cook for a minute, whisking now and then.
Add the milk and the heavy cream. Cook until the mixture thickens, which should take a few minutes.
Combine the two cheeses, which should total about six cups.
Add three cups of cheese mixture to the pan and let the cheese melt.
Once the cheese has melted, remove from the heat and add salt, black pepper, paprika, garlic powder, and mustard powder.
Transfer half the pasta to the baking dish and sprinkle 1 ½ cups of cheese mixture to create the first layer.
Lastly, add the other half of the pasta and top with the remaining 1 ½ cups of cheese mixture.
Bake for 15 minutes and serve hot.