Combine almond flour and oatmeal flour in a large bowl.
Add erythritol, baking powder, salt, and cinnamon, and mix again.
Cut cold unsalted butter into small pieces and mix in by hand until crumbly.
Add almond milk and egg, then gather the dough.
Add nuts and berries (optional) and mix well.
Shape the dough into half-moons and place on a pan.
Bake in a preheated oven at 180°C for 20-25 minutes.