Bring the butter to room temperature. Combine the flour with the matcha and sift 3 times. If the black beans are large, chop in half. Preheat the oven to 180℃.
Whisk the butter in a bowl until soft. Add sugar in 5 batches and mix well until white.
Mix in the beaten eggs in small batches.
Add the sifted powdered ingredients and black beans. Mix lightly with a rubber spatula. Mix until the dough becomes glossy.
Pour into the mold lined with parchment paper, and bake for 35 to 45 minutes in the 180℃ preheated oven. Test the cake with a skewer and make sure it comes out clean.
Story Behind this Recipe
I wanted to make a Japanese-style cake The color is really pretty, and it's great for a gift.
Cool on a rack when it's freshly baked. Cover with plastic wrap when it's cooled slightly. It makes the cake firm. If you coat the black beans with flour (that is, if you mix the flour into the beans), it doesn't sink into the dough. If you're using a 18 cm sized cake mold, multiply the measurements by 1.5.