Preheat the oven to 180°C.
Combine whole wheat flour, baking powder, and salt in a bowl.
Cut cold butter into small pieces and rub it into the flour mixture with your hands until crumbly.
Add erythritol and milk, and gently fold the mixture with a spatula.
Gather the dough, flatten it thickly, and cut into 6 equal pieces.
Place them on a baking tray lined with parchment paper.
Bake in the oven at 180°C for 20~25 minutes.
Let them cool before eating.