Preheat oven to 400 degrees F. Cook and drain macaroni, adding some butter so it doesn’t stick. Melt 4 tablespoons butter in a large saucepan and add flour and salt, whisking to stir until blended. Add milk and cream to pan gradually, stirring constantly. Bring to boiling point and boil 2 minutes, stirring constantly. Reduce heat and cook 10 minutes, stirring constantly. Add shredded cheese little by little and simmer mixture until cheese melts. Take pan off heat and add macaroni and toss to coat. Transfer to a buttered baking dish and sprinkle with buttered baking crumbs. Bake 20 minutes until top is golden brown.