Pour boiling water over the mugwort powder, let it sit for a while, then strain through a tea strainer and squeeze out the water.

Crack the egg into a bowl, add sugar, and whisk lightly until slightly thickened.

Add the oil and mix, then add the squeezed mugwort powder and mix again.

Switch to a spatula, sift in the cake flour and baking powder, and fold gently without kneading.

When about 80% mixed, add the boiled azuki beans and mix until no flour remains.

Pour the batter into the mold, top with chestnuts, and bake in a preheated oven at 350°F (180°C) for 15-20 minutes. It's done when a skewer comes out clean.

Once baked, it won't rise enough to crack, but it will be moist and delicious.

After it cools slightly, cover with a lid or plastic wrap to cool completely.

Cross-section view.