In a soup pot cook macaroni according to the package direction.

Drain and set aside.

In the same pot over medium heat melt butter.

Add flour, salt and pepper, stir to mix well.

Gradually whisk in milk, bring to a boil and cook until thickened stirring constantly.

Stir in Cheddar cheese until melted.

Return macaroni to pot and mix well.

Add mozzarella cheese and cook until cheese is melted and mixture is heated thru.