A risotto is always at its best when first cooked. However, you can store leftovers covered or in an airtight container in the refrigerator for 2 to 3 days. It's important to cool the risotto quickly after cooking by transferring it to shallow containers and refrigerating it promptly. When reheating the leftovers, heat them thoroughly either in the microwave for 3 to 4 minutes or gently on the stovetop with a little extra water or stock until they are piping hot.