If you have a little extra time, you can bake the macaroni and cheese to give it a golden crust. Pour the prepared mac and cheese into a casserole dish, cover with a lid or foil and bake at 325 degrees F for 20 minutes. Remove the cover, sprinkle with breadcrumbs and a few pats of butter and bake, uncovered, until the top is golden and the interior is bubbly, another 10 to 15 minutes.