Preheat oven to 350°F and prepare a baking tray with parchment paper or a silicone baking mat.
In a large bowl, cream together butter, peanut butter, brown sugar, white sugar, vanilla, and egg with an electric mixer on medium speed until well combined (Approximately 1-2 minutes).
4 tbsp butter, 1/3 cup peanut butter, 1/3 cup brown sugar, 1/4 cup white sugar, 2 tsp vanilla, 1 egg
Add flour and baking soda and mix on low speed all is just incorporated and a light and soft peanut butter dough forms.
1 cup flour, 1/2 tsp baking soda
Lightly fold in Reese's cups and mini chocolate chips.
20 Reese's Peanut Butter Cups, 1/2 cup mini chocolate chips
Place into refrigerator for 20 minutes to chill. This is essential so the cookies bake thick, and don't spread out.
Remove from fridge and roll into balls. Place 2 inches apart onto a prepared baking tray.
Bake for 10-12 minutes. Do not over bake. Cookies will look soft but will continue to bake after removing them from the oven and keeping them on the hot tray. After 3-5 minutes transfer them to a cooling rack.
Enjoy!