Heat and melt the white chocolate and butter in a microwave for about 1 minute at 600W. Mix well and leave aside.
Beaten the eggs in a bowl and add with the sugar. Mix until the egg becomes whiter.
Add the chocolate butter with the egg cream and mix thoroughly.
Mix the matcha powder and flour and shift the matcha flour into the butter cream.
Use spatula and mix the butter by cutting motion.
Pour the filling in oven-proof containers and bake them in a preheated oven at 200℃ or 390F for about 8-10 minutes. Be careful not to overcook.
Sprinkle the powder sugar over the Matcha chocolate fondant and serve.