In a mixing bowl combine spelt flour, baking powder, cornstarch, and salt. In a separate mixing bowl mix butter with sugar. Then add the peanut butter and oat milk and stir again.
Leave the dough to rest in the fridge for half an hour or even better for another hour so that you can work well with the peanut butter dough.
Now roll out the dough thicker with a rolling pin and some flour. The dough should not be too thin. Otherwise, the shapes will break easily. Use the cookie cutters and bake the cookies for 8 - 10 minutes.
Now you can be creative and coat the cookies with chocolate or use sprinkles. Be sure to let the cookies cool down.