Do not preheat the oven. There is an hour rest time before making these cookies.

1. Melt together the butter and chocolate chips using a microwave-safe bowl in the microwave for thirty-second intervals, and stirring between each interval until smooth and creamy. You can also use a double boiler over medium-low heat on the stovetop. Stir frequently until the mixture becomes smooth and creamy. Let chocolate cool down for about fifteen minutes.
2. In a separate, medium-sized bowl, measure out the flour, cocoa powder, baking powder and salt. Give the dry ingredients a quick stir with the whisk so that ingredients get dispursed evenly.
3. In a large bowl, combine the brown sugar, eggs and vanilla. Mix together until well combined. Slowly add the dry ingredients in two additions, making sure to scrape down the sides of the bowl with a spatula and incorporate everything well. Add cooled chocolate and continue to mix until just combined.
4. Cover bowl and place in the refrigerator for at least an hour to firm up. If you chill overnight, allow the dough to come to room temperature before shaping into balls.
5. Preheat the oven to 325 degrees. Line baking sheets with parchment paper or silicone baking mat.
6. Scoop out the dough in slightly mounded tablespoon scoops, for reference, my cookie balls weighed approximately 33 grams. Roll it into balls using the palms of your hands, and place onto the lined baking sheet about 3 inches apart.
7. Bake cookies for about 10 to 12 minutes until the tops of the cookies start to crack. While baking, cut the marshmallows in half, and cut down the chocolates so that they are smaller than the marshmallows.
8. Remove cookies from the oven. Carefully place one piece of chocolate onto the top of each cookie and cover with a marshmallow half. Place back in the oven until the marshmallow has softened, about 4 minutes.
9. Remove baking pans from the oven, sprinkle chocolate shavings onto the tops of the marshmallows and let cool on pans for about five minutes. Transfer the cookies to a cooling rack.