Au Gratin Potatoes with a Creamy Sauce Mix

dehydrated potato with preservative, corn starch, maltodextrin, salt, enriched flour wheat flour, niacin, iron, thiamine mononitrate, riboflavin, folic acid, whey, cheddar cheese milk, cheese culture, salt, enzymes, dehydrated onion, potassium chloride, butter, baking soda, dehydrated garlic, natural flavor, color yellow 5, yellow 6, yellow lake 5, yellow 6 lake, buttermilk solids, sodium phosphate, modified corn starch, enzyme modified cheese cheddar cheese milk, cheese culture, salt enzymes, disodium phosphate, enzymes, xanthan gum, lactic acid, disodium inosinate, disodium guanylate