Preheat the oven to 350 degrees Fahrenheit and line several baking sheets with parchment paper.

Mix the sugar cookie mix, dark chocolate chips, and cocoa powder in a large mixing bowl until combined.

Use a hand or stand mixer to beat in the butter and large egg until a thick dough forms, about 2-3 minutes. The dough may not come together initially, but it will keep beating.

Use a 1 ½ Tablespoon cookie scoop to scoop out dough balls and roll them into balls about the size of a golf ball.

Bake each baking sheet individually for 11-14 minutes or until the cookies begin to get firm on the edges.

Top each cookie with ½ of a marshmallow or 3 mini marshmallows, pushing it into the center so the cookie expands slightly.

Bake again for 2-3 minutes or until the marshmallows puff up and take on a golden color at the edges.

Remove the cookies from the oven and allow them to cool on the cookie sheet for at least 5 minutes before removing to a cooling rack or serving plate.

Serve warm with your favorite hot beverage, optional.