Heat oven to 350. Prepare a deep sided 9x13 pan by coating with cooking spray.
Set aside
Bring a large pot of water to a boil. Add salt, and cook macaroni according to directions until tender. Drain and transfer the macaroni to the baking pan.
While the macaroni is cooking. Combine the milk and eggs in a large bowl. Whisk until thoroughly combined. Add the butter, cheeses, sour cream, salt and pepper and sugar and stir til combined. Pour over macaroni and mix well. Top with grated mild cheddar cheese. Bake for 30-45 minutes or until the top is lightly golden brown.