Frozen dumplings need longer cooking time than slightly defrosted ones. I take the dumplings out of the freezer the minute I get home, then in about 10 minutes when I’m ready to start cooking, they are slightly defrosted, just perfect for this recipe.
Alternatively, you can steam dumplings in a bamboo steamer. Place the steamer above a pan with boiling water, a washed lettuce leaf on the bottom, and then place slightly defrosted dumplings in the steamer. Cover and steam for about 10-15 minutes (until they are soft + hot through and through). The lettuce in this scenario serves to prevent the pastry from sticking to your bamboo steamer and never getting off.