Soak the Dried Adzuki Beans in plenty of Water for at least 8 hours or overnight until plump.
Drain the soaked beans, place them in a pot, cover with fresh Water and bring to a boil. Reduce heat and simmer, partially covered, until the beans are very tender and falling apart, about 45–60 minutes; add more Water if needed.
Drain excess liquid (reserve a little cooking liquid), then mash the beans with a potato masher or blend briefly until smoothish. Return the mash to the pot, add Granulated Sugar and a pinch of Fine Salt, and cook over low heat, stirring, until the mixture thickens. Stir in a tablespoon or two of Neutral Oil and continue cooking and stirring until the paste is glossy and holds together; cool completely.
Meanwhile make the dough: in a large bowl combine the All-Purpose Flour, Instant Dry Yeast, Baking Powder, a bit of Granulated Sugar, and a pinch of Fine Salt.
Add warm (not hot) Water and a little Vegetable Oil to the dry ingredients and mix until a shaggy dough forms. Turn out onto a lightly floured surface and knead until smooth and elastic, about 8–10 minutes, or use a stand mixer with a dough hook.
Place the dough in a lightly oiled bowl, cover, and let rise in a warm place until doubled, about 60 minutes.
Punch down the dough and divide into 12 equal pieces. Flatten each piece into a disc, spoon about 1–2 tablespoons of the cooled red bean paste into the center, then gather and seal the edges to form a smooth bun.
Place each bun seam-side down on a small parchment square in your steamer basket. Cover and let the buns proof for 20–30 minutes until slightly puffy.
Bring water to a steady boil in the steamer pot, then steam the buns over medium-high heat for 12–15 minutes. After steaming, turn off the heat and let the buns rest, covered, for 3–5 minutes before opening the lid to prevent collapse.
Serve the red bean buns warm. They’re lovely on their own or with tea.
