Cream softened butter with both sugars until light and fluffy (2-3 minutes)
Beat in the egg and vanilla
In a separate bowl, whisk together flour, cocoa powder, baking soda, and salt
Add the dry ingredients to the wet ingredients and mix just until combined
Fold in the chocolate chips
Chill the dough for at least 30-60 minutes
Scoop about 2 tbsp of dough for each cookie, roll into a ball, and place on a parchment lined baking sheet leaving ample space between each cookie
Bake at 350°F (175°C) for 7-8 minutes
Take out of the oven and place the marshmallow halves in the middle of each cookie
Bake for 2-3 more minutes until edges look set and middle is still soft
Optional: While still warm, place a round object over the cookies and spin gently to round the edges and create a perfect circle
Cool for 5-10 minutes before transferring to a wire rack or plate
Drizzle the cookies with melted chocolate and top with Christmas sprinkles
Enjoy
