Preheat oven to 350 degrees F and line two baking sheets. Using the food processor, take ½ cup of the Reese’s mini peanut butter cups and pulse. Set aside.
In the bowl of a stand mixer, combine the sugars, butter, and shortening. Mix on a low speed until well combined. Add vanilla and egg to the sugar/butter mixture, beat again until incorporated. In a separate large bowl combine the flours, baking soda and baking powder. Slowly add the flour mixture to sugar/butter mixture in three separate batches on low.
Add the peanut butter, the ½ cup of chopped Reese’s peanut butter cups, and the remaining ½ cup of whole peanut butter cups to the cookie batter. The mixture should be crumbly. Slowly add about ¼ cup of whole milk, until the mixture comes together and resembles a soft dough.
Scoop out round teaspoon amounts of dough onto the prepared cookie sheets. In total, this recipe should make about 3 dozen cookies. Bake for about 10-12 minutes, and let cool on a cooling rack before serving. Enjoy!!