Daifuku Mochi (Red Bean Mochi)

Steps

1. Divide the anko into 8 portions of 30 g each and roll each into a ball between slightly damp palms. Set them on a plate and refrigerate for 15 minutes: firm balls are easier to wrap without squashing.
2. Set up your work surface: generously dust a sheet pan or board with potato starch through a sieve, and keep a small bowl of starch within reach for your fingers.
3. In a microwave-safe glass bowl, mix the glutinous rice flour and sugar. Pour in the water in a thin stream while whisking until you have a smooth, runny batter, like thick heavy cream, with no lumps at all.
4. Microwave method (800 W): cover the bowl with a plate or loosely laid plastic wrap and heat for 1 minute. Stir hard with a wet spatula: the edges have set while the center is still liquid. Heat for another minute and stir again, then 30 seconds to 1 minute more. The dough is done when it's completely translucent, slightly shiny, with no opaque white spots, and forms an elastic mass. At 1,000 W, cut each burst by 10 seconds.
5. Steamer method, if you don't have a microwave: pour the batter into a heatproof bowl, set it in a steamer basket over rapidly boiling water, cover, and steam for 20 minutes. Stir with a wet spatula after 10 minutes. The cue is the same: completely translucent, elastic dough.
6. Work the hot dough for 30 seconds with the wet spatula, folding it over itself: it turns smooth and stretches into long ribbons. Turn it out onto the starch and dust the top as well. Let it cool for 2 to 3 minutes, just enough to handle: it needs to stay warm to seal.
7. With a starch-dusted bench scraper, divide the dough into 8 equal pieces. Flatten each piece between your fingers into a 3-inch (8 cm) disk, thinner at the edges than in the center, brushing the starch off the side that will face inward.
8. Set a ball of anko in the center of a disk. Bring the edges up, stretching them gently around the filling, pinch them together to close, then turn the mochi seam side down and roll it between your palms to round it. Repeat with the rest.
9. Brush off the excess starch with a dry pastry brush. Serve the daifuku at room temperature within a few hours; cut one in half with a clean, dry knife to show off the filling.