A Southern sideboard is truly a beautiful sight to withhold. Whether it’s filled with sweet potato, green bean, and mashed potato casseroles on Thanksgiving or cole slaw, baked beans, and potato salad at a backyard cookout, Southern cooks have mastered the sideboard. This Macaroni Au Gratin is a totally decadent mixture of two of our favorite sideboard mainstays—macaroni and cheese and au gratin potato casserole. With just four ingredients (plus salt and pepper), you can have a cheesy, bubbly casserole on the table for your family to devour. For the best texture for your Macaroni Au Gratin, our Test Kitchen has two tips: First, use block cheese and shred it yourself instead of buying a bag of shredded cheese. The few extra minutes it will take are worth it. Second, even though you’ll be tempted to dig in as soon as you remove it from the oven, don’t ignore the recommendation to wait 15 minutes before serving. This allows the Macaroni Au Gratin to set to the perfect texture for serving. This Macaroni Au Gratin is going to be a hit with kids and adults alike. You can never go wrong with a crowd-pleasing, cheesy pasta bake, so this casserole recipe will soon become your go-to for holidays, potlucks, new neighbors, and weeknight dinners.