Preheat oven to 350°F and line cookie sheet with parchment paper. Next, in a bowl, combine the butter and sugar.
Beat on medium speed until light and fluffy. Add eggs one at a time scraping the bowl as needed.
Mix cocoa powder, flour, salt, baking, powder, and espresso. Mix with butter mixture.
Mix the ingredients until well combined. Stir in the chocolate chips.
Next, scoop a heaping tablespoon of dough, roll into a ball and place on the cookie sheet. Using the palm of your hand, slightly flatten the ball.
Bake the cookies for 12 minutes. Remove from oven and place a marshmallow half on each cookie. Bake for an additional 2-4 minutes.
Let the cookies cool on the cookie sheets 5-10 minutes, then transfer to a wire rack to cool completely.