Preheat Oven to 375 degrees. Lightly grease your baking pan and set aside.
Bring a large pot of water to a boil with salt. Add your spaghetti and cook for about 6 minutes. Drain and set aside. You want your pasta to be slightly undercooked since it will cook in the oven.
Melt your butter in a large saucepan. Add the flour and whisk for 30 seconds.
Add your Salt, Black Pepper, Granulated Garlic and Cayenne Pepper. Whisk until combined.
Slowly add your Half and Half. Whisk until smooth. Add your Heavy Cream and continue to stir. Bring to a boil and then reduce heat to simmer. Allow to simmer until it begins to thicken.
Remove from heat and stir in half of your Mozzarella and Cheddar Cheese.
Add your spaghetti to the cheese sauce. Stir until noodles are coated.
Pour into your greased baking pan. Top with the remaining cheese and bake for 25-30 minutes.
*Nutritional information is a calculated guesstimate. Please note that this can change with different brands and modifications you may make to the recipe. For the most accurate information, use a nutritional calculator with the exact brands and measurements you're using with each recipe.