Cook pasta according to package directions; rinse, drain and set pasta aside.

Using a large skillet, add butter and place over medium heat.

Once butter has melted, add flour and cook for 3-4 minutes, stirring constantly. (Note: The flour will turn light golden brown in this step.)

Add milk, stirring constantly as you pour milk into skillet.

Add salt, pepper, garlic powder and mustard powder; whisk until well combined.

Once milk is hot, add cheeses and whisk until fully melted and smooth.

Add cooked pasta and stir until well coated.

Simmer for 5-6 minutes, stirring occasionally, until mixture has thickened and most of the milk has evaporated.