Bring a large pot of salted water to a boil and cook the macaroni until just tender but firm to the bite, then drain and set aside.
Melt the butter in a saucepan over medium heat, then whisk in the flour to form a smooth paste, cooking it for about a minute.
Slowly pour in the whole milk along with paprika, salt, black pepper, and ground mustard while constantly whisking, cooking the sauce until it thickens to your preferred consistency, usually between 1 and 2 minutes.
Take the saucepan off the heat and fold in the shredded gruyere and sharp cheddar cheeses until they are fully melted and blended.
Stir the drained macaroni into the cheese sauce until everything is evenly coated, then remove from heat and serve right away.