1½ cups plus 2 tablespoons all-purpose flour
6 tablespoons Dutch-process cocoa
½ teaspoon baking soda
½ teaspoon coarse salt
6 tablespoons unsalted butter, at room temperature
¼ cup plus 2 tablespoons creamy peanut butter
½ cup sugar
½ cup brown sugar
1 large egg
1 teaspoon vanilla extract
2 tablespoons milk
2 cups coarsely chopped peanut butter cups, divided (Frozen for at least 30 minutes)
Heat oven to 350º. Line baking sheets with parchment or nonstick baking mats. In a medium bowl, whisk together the flour, cocoa, baking soda and salt.
In the bowl of an electric mixer, beat the butter, peanut butter and sugars on medium speed until light and fluffy, 1-2 minutes. Add in the egg and vanilla and milk and beat until smooth. Reduce mixer speed to low and gradually add in flour mixture. Beat just until combined. Using a spatula, gently fold in 1½ cups of the peanut butter cups.
Scoop the dough onto the prepared baking sheets, spacing about 2 inches apart. Gently press a few pieces of the reserved peanut butter cups onto each ball of dough.
Bake for 11-14 minutes, depending on the size of your cookies. The cookies should feel soft when they come out of the oven and will set as they cool. Allow to cool on the baking sheets for 10 minutes, then transfer to a wire rack to cool completely. Store in an airtight container.