Step 1

Spoon tablespoons of bean paste onto a parchment-lined tray or baking sheet. Cover and freeze for 1 hour. Shape into balls; set aside. In a medium heatproof bowl combine the rice flour and sugar. Stir in water.

Step 2

Place bowl in a steamer basket set over simmering water in a large pot. Place a kitchen towel over the bowl and add the lid. Steam for 20 minutes. (Or, cover bowl with vented plastic wrap and microwave on 100% power (high) for 3 minutes. Stir; cook 30 seconds more.)

Step 3

Sprinkle cornstarch over a work surface. Turn out dough over cornstarch. Let stand at least 10 minutes or until dough is cool enough to handle. Use cornstarch to dust your hands and top of dough. Lightly work dough with hands until it cools to room temperature. Divide dough into 12 pieces.

Step 4

Shape and flatten each dough piece into a round, using cornstarch to dust hands and dough as needed. Make an indent in the center of each. Place a ball of bean paste onto center of each round. Shape dough around filling into a smooth ball. Store in an airtight container in a cool dry place up to 2 days. For longer storage, freeze in an airtight container.