Cook macaroni according to instructions on box and the set aside. Preheat oven to 400°. Over medium heat in a large lightly oiled cast iron skillet, brown onions and garlic. Add butter and allow to completely melt. Stir in flour until a roux forms. Stir in half & half, milk, salt, pepper, and basil. Add cream cheese. Stir in mild cheddar cheese, four cheese blend, parmesan cheese, and 1 cup sharp cheddar cheese. Mix in macaroni. Top with remaining 1 cup sharp cheddar cheese. Bake for 20 minutes. Serve while still warm.