Scoop about 1 tablespoon (20 g) of red bean paste and roll it into a ball. Repeat to make 10 balls.

Place the anko balls on a parchment-lined plate and refrigerate while you prepare the mochi.

In a microwave-safe bowl, whisk together the glutinous rice flour and sugar. Add the water and stir until smooth.

Loosely cover the bowl with plastic wrap. Microwave on high for 1 minute.

Remove and stir with a wet spatula. Cover loosely and microwave for 1 more minute.

Stir again, cover, and microwave for a final 30 seconds. The mochi should change from bright white to slightly translucent and cream-colored. If white patches remain, microwave in 20-second intervals until translucent.

Whisk together the flour, sugar, and water in a heat-safe bowl. Set up a steamer and wrap the lid with a clean kitchen towel to prevent condensation from dripping in.

Place the bowl in the steamer basket, cover, and steam for 15 minutes. Stir with a wet spatula halfway through. The mochi is done when it turns translucent.

Generously dust your work surface with potato starch or cornstarch. Use a wet spatula to transfer the hot mochi onto the starch. Sprinkle more starch on top and let cool for 2 to 3 minutes.

Dust your hands with starch and divide the mochi into 10 equal pieces using a starch-dusted knife or bench scraper.

Flatten one piece into a 3-inch (8 cm) disc in your palm, keeping the center slightly thicker than the edges.

Place a chilled anko ball in the center. Pull the mochi edges up and around the filling, stretching gently, then pinch all edges together at the top to seal.

Place seam side down on a starch-dusted surface. Repeat with remaining pieces.