Preheat your oven to 375ºF.
In a stand mixer, combine the creamy peanut butter and softened salted butter. Beat until well blended.
Add the packed dark brown sugar, baking soda, and baking powder. Beat until combined. Incorporate the egg and vanilla extract.
Gradually add the all-purpose flour and mix just until combined. Stir in the quartered miniature Reese's peanut butter cups and mini chocolate chips.
Scoop out portions of dough onto parchment-lined baking sheets, spaced apart.
Lightly press down on each cookie dough ball using a glass dipped in sugar.
Bake for about 10 minutes, keeping an eye on them to avoid overbaking.
Allow cookies to cool on the baking sheet for about 3–5 minutes before transferring to a cooling rack.
Melt the chocolate chips for optional drizzle and drizzle over cooled cookies.
Store cookies in an airtight container.