Filling - Combine kidney beans, water and sugar together in a small pot. Bring to boil at medium heat and simmer at low heat for about 5 minute till kidney beans softened . Mash kidney beans with a spoon or rubber spatula or blend to smooth if you prefer. Set aside to cool.
Preheat oven to 200 deg C. Sift both flours and matcha powder together and set aside. Line a 8 x 12 inch rectangle cake pan with parchment paper.
Melt butter in a pot, keep warm and set aside.
Whisk egg whites until foamy at low speed. Then add sugar in 3-4 batches and beat until egg whites are glossy and stiff peaks form.
Add egg yolks in batches and fold lightly with a rubber spatula. Sift the flour the second time into the yolk mixture and fold gently, then add warm melted butter and fold through.
Pour batter into prepared cake pan and spread evenly with a palette knife. Bake for about 10-12 minutes.
When cake is done, unmould from pan and leave to cool.
Place matcha sponge cake on a plastic sheet or parchment paper, cake surface facing up (with a dry cloth placing beneath the plastic sheet to prevent slip while rolling the cake).
Whisk fresh cream to peak form and spread on to sponge cake followed by the mashed kidney bean paste on top.
Gently roll up the matcha sponge cake to make a Swiss roll and chill it for a few hours or overnight.
Trim the sides of the cake roll and dust with icing sugar or snow powder on top of cake before serving.