Mix the soup ingredients (hot water, gelatin powder, chicken soup stock) in a heatproof container. Let it cool and refrigerate until set.

Finely mince the green onion.

In a bowl, combine the filling ingredients (ground pork, minced green onion, grated garlic, grated ginger, sake, oyster sauce, salt, pepper, sesame oil) and the prepared soup jelly. Mix until sticky.

Place the filling mixture onto the center of each gyoza wrapper. Wet the edges with water and fold into a pleated pouch.