Whisk flour, cocoa, baking soda, and salt in a small bowl. Set aside.
Beat butter and sugars in the bowl of a stand mixer fitted with the paddle attachment until light and fluffy (approx 3mins).
Add Reese Peanut Butter Chocolate Spread and beat until combined.
Add egg and vanilla and beat until well combined (approx 1 min).
Reduce mixer to low and add flour mixture. Mix until just incorporated.
Add peanut butter chips and mix until just incorporated.
Using a large cookie scoop, portion the dough into 16 mounds. Round the mounds into balls and press down slightly to flatten.*
Place mounds on a tray, cover with plastic wrap, and refrigerate at least 3 hours. Do not bake unchilled dough! Cookies will spread too much.
Preheat oven to 350F. Line a baking sheet with parchment or a Silpat.
Place cookies on baking sheet at least 3" apart. I use a half sheet pan and baked 6 cookies per sheet.
Bake for 11-14minutes or until cookies start to crack.**
Cool on baking sheet for 10mins and transfer to a cooling rack to cool completely.
Notes
*The dough will be quite soft at this point, I placed the scooped balls in the fridge for 15mins to firm up before rounding. **If you prefer fluffier cookies, bake for around 11mins, before cracking.