Preheat oven to 350 degrees
Cook macaroni according to package directions. Drain and place macaroni in a greased 9x13 baking pan
In a medium saucepan, melt 4 tablespoons butter on medium-low heat. Add in the flour, salt and sugar. Stir until smooth
Gradually add in the milk, stirring constantly. Bring to a boil; cook and stir for 2 minutes or until the mixture has thickened. Reduce heat to low
Stir in the Velveeta cheese until melted
Stir in cottage cheese, sour cream and one cup cheddar cheese until melted
Pour the cheese mixture over macaroni. Sprinkle with the remaining cheddar cheese
Melt remaining butter and toss with bread crumbs; sprinkle over top of the casserole
Bake uncovered at 350° for 30 minutes or until golden brown
