Mix the matcha powder with the flour. Leave aside.
Warm up and soften the butter and half of the white chocolate chips in a microwave for about 20 seconds.
Add the sugar and egg with the butter chocolate cream and mix until all the ingredients incorporate.
Add the matcha mixed flour with the buttercream and mix well.
Add the reserved white chocolate chips with the cookie dough and mix.
Cover up the dough with a plastic wrap and let it sit for about 30 minutes in a refrigerator.
Take a bunch out of the dough and roll it up with your hands.
Put the cookie ball on a baking sheet and press center with your thumb to make a flat cookie.
Repeat to make more cookies.
Bake the cookies in a preheated oven at 170°C or 340°F for about 20 minuites.
Cool down the cookies at room temperature and serve.