Preheat oven to 425. If your mac n cheese is cold, nuke it for about 30-60 seconds until soft enough stir. Split bagel into two halves,
Top each bagel half with 2-3 spoonfuls of mac n cheese. Top with bacon, cheese and a little bread crumbs if desired. Place in the oven for 7-10 minutes until cheese is nice and melted. Remove from oven and let rest for about 1 minute.