Using a food processor, grind the peanuts until coarse. Add the powdered sugar and peanut butter and continue mixing for 2 minutes, scraping down the sides as needed, until a compact paste is formed.
Remove the peanut mazapan mixture from the food processor. Using a rolling pin, roll out the dough to 3/4-inch thick. With a 2-inch round cookie cutter, cut out circles of dough and carefully remove them onto a baking sheet lined with wax or parchment paper. You can reform and roll the dough again to yield the remaining rounds.
Serve immediately, or wrap in parchment paper and refrigerate to store.