Place the semi-sweet chocolate chips in a double boiler over low heat, stirring occasionally until melted and smooth.
In a bowl, whisk together the flour, cocoa powder, baking powder and salt.
In a large bowl, or the bowl of a stand mixer, combine the butter and brown sugar and beat together until smooth.
Add in the eggs, one at a time, scraping down the sides of the bowl as needed. Beat in the vanilla.
On low speed, add in the melted chocolate and the dry ingredients.
Stir in the chopped peanut butter cups and peanut butter chips.
Cover the bowl and let the dough sit at room temperature for 30-45 minutes to allow the chocolate to set up.
Preheat the oven to 350ºF. Line several baking sheets with parchment paper or silpat liners.
Roll the dough into tablespoon sized balls and place on the prepared baking sheet, 2 inches apart.
Bake for 10-11 minutes. The cookies will still be soft in the middles, but will continue to set up when cooled.
Let the cookies cool on the baking sheet for 5 minutes before removing to a cooling rack to cool completely.
