Put butter into a bowl. Cover with plastic wrap and microwave to melt. Add vegetable oil and mix well. Also add the egg and mix.
Add sugar and whisk well. Then add the milk and continue to mix.
Combine cake flour and matcha and sift. Add a third into the bowl and mix well.
Using a rubber spatula, add the rest of the powdered ingredients into the bowl and mix lightly. Add the black beans before everything is nice and smooth. Mix lightly.
Line a muffin pan with parchment paper. Fill about 70-80% of each mold with the batter. Bake in a 180℃ preheated oven for 18-20 minutes.
When they're done, test with a skewer and make sure it comes out clean. Done! Cool on a rack before serving.
Cross-section: Note the chunky black beans You can smell the matcha too.
Story Behind this Recipe
Because I had leftover matcha, I used it with the black beans left in the fridge to make this Japanese-style muffins. It's different from azuki beans and also very tasty.
Make sure to mix lightly with a rubber spatula after adding the powdered ingredients and the black beans! If you mix too much, it won't get fluffy when baked! Please adjust the baking time to your oven if it doesn't seem baked enough after the instructed time. You could also scatter black beans (not listed) on top before baking - it will look nice.