Preheat oven to 350F and line two baking sheets with silpat mats or parchment paper.
Combine peanut butter, flour, brown sugar, egg into a large bowl and mix until smooth dough forms. Stir in chopped up peanut butter cups. Take 2 tbsp of dough, roll into a smooth ball between palm of your hands.
Place on baking sheet and then push down gently with palm of hand to form a thick round disk. Cookies will not spread much during baking so make sure the cookie dough is smooth and round and slightly less than 1/2 inch in thickness.
Bake for about 10 minutes until cookies are set.
Let cookies finish cooling on cookie sheets so that cookies can finish setting. Once cookies are firm, remove and enjoy.
