Preheat the oven to 180°C.
Combine almond flour, coconut flour, baking powder, and salt in a bowl.
In a separate bowl, mix melted butter, erythritol, eggs, vanilla extract, and matcha powder.
Combine the wet and dry ingredients to form a dough.
Mix in the dark chocolate and walnuts evenly throughout the dough.
Scoop the dough onto a baking pan and shape it into rounds.
Bake in the preheated oven at 180°C for 13–15 minutes.
Cool completely before serving.