Cook the macaroni according to the package instructions. Drain and set aside.
In a medium saucepan, add the butter and slowly melt over low heat. Add flour to the melted butter and stir until well incorporated and mixture thickens.
Turn burner up to medium heat and slowly add the milk, about a half cup at a time. Continue to stir the sauce until it begins to lightly simmer and thicken. Then, add seasonings and mustard.
Remove sauce from heat and add the cheddar and parmesan cheese. Stir until the cheese is completely melted.
Pour macaroni into cheese sauce and stir to combine. Enjoy!