Preheat your oven to 350°F (175°C) and grease a square baking pan.
In a large mixing bowl, combine the melted butter and granulated sugar. Mix until well combined.
Add the eggs one at a time, beating well after each addition.
Stir in the vanilla extract.
In a separate bowl, sift together the flour, cocoa powder, matcha powder, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until combined.
Add in the chocolate chips and chopped mint leaves.
Pour the batter into the prepared baking pan and spread it evenly.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Allow the brownies to cool in the pan for at least 10 minutes before slicing and serving.