- Preheat the oven to 350F then line a baking sheet with parchement paper and set aside. 
- Cream the butter, peanut butter, brown sugar, and granulated sugar. Add in the eggs and vanilla extract then mix until combined. 
- Add in the flour baking powder, baking soda, corn starch, and salt, and mix just until the flour mixture disappears. Gently fold in the roughly chopped-up Reese's peanut butter cups.  
- Using a large cookie scooper, scoop out 9 equally sized cookie dough balls, roll them in between the palm of your hand, then gently flatten them to about 1 inch then freeze the cookie dough discs for 15 minutes. 
- Bake the cookies in the preheated oven for 12-13 minutes 
- Melt the peanut butter chips with the oil in the microwave in 30 second increments, mixing in between every time.  
- Generously top each hot cookie with the melted peanut butter chips, spread it all around, then top with the chopped-up Reese's cups. Let the cookies cool down fully on the baking sheet then enjoy!