Mix oat flour, almond flour, baking powder, and salt in a bowl.
Add protein powder, erythritol, and Greek yogurt to the bowl and knead the dough.
Chop dark chocolate into small pieces and fold into the dough.
Shape the dough into cookies and place them on a baking tray.
Bake in a preheated oven at 180°C for 12-15 minutes.