Line baking sheets with parchment paper or silicone baking mats. Cream the butter and sugar on medium-high speed until light and fluffy, about 2-3 minutes. Blend in the eggs one at a time, scraping down the bowl as needed.
Mix in the cocoa powder at low speed until well blended.
Add the flour, salt and baking powder to the bowl and mix on low speed just until incorporated. Stir in mini peanut butter cups.
Scoop up about 2 tablespoons of dough and place on the prepared baking sheets, and repeat process, placing balls about 2 inches apart.
Bake about 12 minutes, until cookies are cooked and slide easily off of parchment paper.