Preheat oven to 350 degrees F.
Line a baking sheet or two with parchment paper.
Using a mixer, cream butter until light and creamy for 2 minutes.
Add in sugar and continuing creaming for 1-2 more minutes.
Add in egg, mixing until fully incorporated into batter.
Add in vanilla extract and mix.
Sift in flour, baking powder and cocoa powder into the mixture, add salt and beat together just until a chocolate dough forms.
Then fold in the mini peanut butter cups, saving some for the tops of the cookies to press in.
Using a medium cookie scoop, (1 & 1/2 tablespoons), scoop cookie dough onto baking sheet and press some peanut butter chips on top
Leave room for the cookies to spread very slightly.
Bake for approximately 10-12 minutes. Cookies will continue baking.
Cookies should be starting to firm up but still soft in the middle. Remove from the oven and press a few more peanut butter chocolate chips and peanut butter cups on top if desired.
Let cookies set on cookie tray for a couple of minutes before removing them to cool completely on a wire rack.
Allow to cool completely prior to storing.