Reese's Peanut Butter Cookies

Preheat oven to 350°F. Line two baking sheets with parchment paper.
Combine the flour, baking soda and salt in a medium bowl. Set aside.
In the bowl of a stand mixer, beat the butter, peanut butter and sugars, until light and fluffy. Add in the egg and vanilla.
Gradually add in the flour mixture on low speed. Stir until dough forms. Then fold in the mini peanut butter cups by hand.
Using your hands, form balls of dough with 2 heaping tablespoons of dough. Gently flatten cookie dough (to form a disk shape) and place on prepared baking sheets.
Bake for 10 to 12 minutes, until the edges are set, and remove from oven. Immediately press a full size peanut butter cup into the center of each cookie. The cookies will still look soft in the center when you take them out of the oven, but they will firm up as they cool.
Let cool for 10 minutes, before transferring cookies to a wire rack to cool completely. The chocolate on the peanut butter cups will take over an hour to fully re-harden. If you are in a rush, you can place the cookie sheets in the fridge to speed up the cooling process.