Prepare mac and cheese according to the box instructions then place in a mixing bowl.
Add sour cream and egg to mac and cheese and stir. (If your mac and cheese is hot you will want to stir right away and quickly to make sure the egg does not cook before getting mixed well)
Fill a muffin tin by adding a spoonful of mac and cheese to each place. Top with bread crumbs and then shredded cheese (Just a pinch of each).
Bake at 350 degrees F for 30 minutes. Allow to cool and then remove from muffin tin.