Combine almond flour, coconut flour, baking powder, and salt in a bowl.
Cut the butter into pieces, add to the bowl and mix with your hands until a crumbly texture forms.
Add erythritol, egg, and almond milk, then knead to form a dough.
Spread the dough into a round shape and cut into 6–8 pieces.
Bake in a preheated oven at 180°C for 20–25 minutes.