Melt white chocolate and butter (○) in the microwave and sift the cake flour, cornstarch and matcha (◇) together. Make a moist and glossy meringue with the egg whites and sugar (☆).
Preheat the oven to 320°F/160℃. Whisk egg yolks and 35 g sugar (★) together in a bowl.
Add chocolate butter mix (○) and flour/matcha mix (◇) in that order into the Step 2 mixture and mix together. Then add the meringue, 1/3 at a time, and fold after each addition.
Pour the batter into the pan and bake in the preheated oven for 40-50 minutes.
Dust powdered sugar over for decoration. It'll give it a nice look.