Mix the matcha powder with the flour and baking powder. Leave aside.
Warm up and soften the butter in a microwave for about 20 seconds and mix with the peanut butter and sugar. Mix well until all the ingredients incorporate.
Add the egg with the buttercream and mix well.
Add the matcha flour with the egg buttercream and mix until it becomes cookie dough.
Take a bunch out of the cookie dough and roll it up with your hands.
Put a cookie ball on a baking sheet and press center with a fork to make a flat cookie.
Repeat to make more cookies.
Bake the cookies in a preheated oven at 180°C or 350°F for about 20 minutes.
Cool down the cookies at room temperature and serve.