Preheat the oven to 375°F
Cook elbow macaroni until just al dente
Drain the pasta and set aside
Melt butter in a saucepan over medium heat
Whisk in flour and cook for 1 to 2 minutes
Slowly whisk in milk until smooth
Cook until the sauce thickens
Stir in salt, pepper, and mustard powder if desired
Add shredded cheddar and any other cheese you like
Stir until the cheese is fully melted
Combine the cheese sauce with the cooked macaroni
Pour the mixture into a greased baking dish
Top with extra cheese or breadcrumbs if desired
Bake for 20 to 25 minutes until bubbly and golden
Let it rest for a few minutes before serving