Preheat the oven to 375 degrees F (190 degrees C). Grease cookie sheets. 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 1/4 inch thickness and cut into shapes using cookie cutters. Place 2 inches apart onto the prepared cookie sheets.
Bake for 20 minutes in the preheated oven, or until lightly brown. Remove from cookie sheets to cool on wire racks.