Preheat oven to 375 degrees F (190 degrees C). Line a cookie sheet with parchment paper.
Melt the chocolate pieces until smooth in a microwave or double burner. Let cool slightly.
In the bowl of a countertop mixer fitted with the paddle attachment, cream together the butter, granulated sugar, and brown sugar until fluffy and light in color.
Add the eggs and Kahlua Peppermint Mocha; beat until liquids are absorbed.
Sift in the flour, cocoa powder, baking powder and salt. Beat until fully combined. (Note: this cookie dough is very sticky!)
Scoop out a rounded tablespoon of dough and gently shape into a flat disc. Place on a parchment-lined sheet pan, leaving about 2 inches between cookies. (Tip: Keep your hands dusted with flour as it will help shape the sticky dough into cookies.)
Bake at 375 degrees F for 5 minutes.
Remove the pan from the oven and gently press 4 or 5 peppermint pieces into the top of each cookie. Return the cookies to the oven and continue baking for another 4 minutes.
Place sheet on rack; allow cookies to cool before removing from pan.