You can either steam or microwave your leftover dumplings. Place the leftover edamame dumplings in a steamer basket or on a heatproof plate. Set up a pot or a steamer with water and bring it to a boil. Once the water is boiling, place the steamer basket or plate with the dumplings on top and cover with a lid. Steam the dumplings for 5-7 minutes or until they are heated through. Microwave the dumplings in 30-second intervals on medium power, checking after each interval to ensure they are heated through.