Preheat the oven to 180°C.
Mix room-temperature butter and sugar until smooth.
Add the egg and mix well.
Sift cake flour, matcha powder, and baking powder into the mixture and knead the dough.
Shape the dough into bite-sized pieces and place them on a baking tray.
Bake in the 180°C oven for 12 minutes, then let the cookies cool.
Place vanilla ice cream on top of the cookies.