Preheat the oven to 350 degrees.
Cook the macaroni until the noodles are al dente.
In a saucepan over medium heat, melt the butter.
Sprinkle the flour into the saucepan with the butter, and stir to combine well. Saute for 1 minute.
Pour in the milk and heavy whipping cream.
Add the garlic powder and salt and pepper to taste in the saucepan. Simmer until the mixture thickens.
Mix the cheeses into the sauce, and stir until completely melted and smooth.
Pour the cheese sauce over the noodles, and stir to combine.
Spread the mixture into a 9x13 baking dish.
Bake for 20 minutes, turn the heat to low broil, and bake another 5 minutes until browned on top.