This loaded mashed potato casserole is a perfect make-ahead side dish for a holiday season and feeds an army! Everyone goes for seconds for this one.
Make-Ahead Note: The casserole can be made ahead through step 8. Cover the baking dish with mashed potatoes and refrigerate for up to 5 days. When ready to bake, bring it to room temperature on a counter for about an hour. And continue with step 9. Store the cooked bacon separately.