It's all about the sauce-to-dry ingredient ratio for this one. Follow the recipe amounts carefully to get a creamy, saucy bake. If you add extra pasta or chicken, your casserole might come out dry. Another tip is to not overbake. Remember that all the ingredients are fully cooked when they hit the oven, so you don't need more than a 20-minute bake to attain golden, bubbly perfection. Bake longer than that, and you risk drying out your casserole.