Preheat the oven to 190 C / Gas mark 5. Grease baking trays. Stir together the flour and baking powder; set aside.
In a medium bowl, mix together the peanut butter and milk. Stir in the flour mixture until well blended. Turn out dough onto a lightly floured surface and knead until smooth. Roll out to 1cm thickness and cut into shapes using biscuit cutters. Place 2cm apart onto the prepared baking trays.
Bake for 20 minutes in the preheated oven, or until lightly brown. Remove from baking trays to cool on wire racks.