Line the cake tin with parchment paper. Cut the butter into 1 cm dice and chill in the refrigerator.
Sift the cake flour. Combine the butter, flour and granulated sugar until it's the consistency of fine panko, using the same produce you would use to make scones.
Add the milk, and mix with a rubber spatula until crumbly.
Press the mixture firmly into the cake tin with your fingers. Bake at 180°C for 25 minutes.
Sift the ☆ cake flour and ☆ baking powder into a bowl. Add the other ☆ ingredients and mix with a whisk (don't beat it though).
Pour this on top of the baked crust, and bake for another 20 minutes. If the top is browning too much, cover with a sheet of aluminum foil.
Take it out of the oven and let it cool down completely before taking it out of the pan. Dust with lots of powdered sugar using a tea strainer. Slice off all 4 edges (check the taste) and cut into 9 squares.
It looks pretty if you decorate the top with a little grated yuzu peel.
Story Behind this Recipe
I wanted the cookie part to be quite thick, and the rich topping part to be fairly thing...that was the balance I was aiming for.
The yuzu juice is not used. Use it in hot pots, or mix with honey and hot water and enjoy as a drink. This tastes better the next day than when it's freshly baked.