Soak the gelatin in water for 5 minutes to bloom. Blend the cooked red beans with water until very smooth.

Pour the red bean mixture into a pot and cook until it thickens slightly. When you lift the spoon, the mixture should fall off in ribbons. Add the gelatin and stir until dissolved. (Optional: Add 2 teaspoons Japanese red glutinous rice flour for a deeper red color.)

Place the glutinous rice flour in a mixing bowl. In a pot, dissolve the all-purpose flour in water.

Cook the flour mixture until it turns translucent, then pour it into the bowl with the glutinous rice flour. Knead until you get a smooth, elastic dough. If the dough is too dry, add a little boiling water as needed. Let the dough rest for 15 minutes.

Once the filling is set, shape it into small balls. (Tip: Work with a little filling at a time to prevent it from softening too much.) Flatten a piece of dough, wrap it around the filling, and seal.

Bring a pot of water to a boil. Drop the dumplings in and cook until they float to the surface, then let them cook for another 2 minutes. Remove and place them in a bowl of cold water.