Cook the macaroni according to package instructions until al dente. Drain and set aside.
In a large saucepan, melt 1/2 cup of unsalted butter over medium heat. Stir in flour for about one minute or till it's smooth without any lumps.
Gradually whisking while continuously adding the milk to prevent forming clumps
bring this mixture up to a simmer and keep stirring until thickened, which should take around 2-3 minutes.
Remove from heat. Stir in grated cheddar cheese (make sure it's sharp) and season with salt as needed till the sauce is creamy.
Combine pasta with half of this bΓ©chamel mixture until coated, then transfer to a serving dish.
Pour remaining bechamel over top
sprinkle additional grated cheese on it. Dot 1 tablespoon unsalted butter and drizzle two teaspoons milk across the surface.
Broil in preheated oven at its highest setting for about 2-3 minutes or until bubbly, being careful not to burn.
Serve immediately.