In a microwave-safe mug, lightly whisk together the egg yolk, sugar, oil, milk, and vanilla extract. (I used a pair of chopsticks to do this).
Sift in the matcha powder, cake flour, and baking powder.
Mix until everything is combined.
Place the mug into the microwave and cook for approximately 60-90 seconds (depending on your microwave's power), or heat until cake is set in the middle.
Cool for 2-3 minutes before serving.
Garnish with whipped cream, powdered sugar, or fruit if you wish.