Preheat the oven to 350 degrees. Line 2 baking sheets with parchment paper and set aside.
Melt the semisweet chocolate and set aside to cool. Whisk together the flour, cocoa, baking powder, baking soda, and salt. Set aside.
Place the butter and sugar into a mixing bowl. Beat together for 3 minutes, scraping the bowl down as needed. Add the egg and vanilla. Mix in the melted chocolate. Blend in the dry ingredients, followed by the milk. Lastly, add the chopped peanut butter chips.
Use a small cookie dough scoop (approximately 2 teaspoons) to shape the cookies. Scoop dough onto the prepared baking sheet. Bake in the oven for 12 minutes, rotating the pan front to back and top to bottom halfway through. Remove from the oven and cool the cookies on the baking pans.