After the water evaporates, the dumplings are cooked, uncovered, to crisp up the bottoms, before being served browned side up. This recipe makes a lot of dumplings, but they freeze well.
Sprinkle with the sesame seeds. Place half the dumplings in a steamer lined with non-stick baking paper. Place over a wok or large frying pan filled with simmering water and steam for 6 minutes.