Preheat oven to 350 degrees F. Line a large baking sheet with a Silpat baking mat or parchment paper. Set aside.

In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt. Set aside.

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugars on medium high speed until light and creamy, about 2 minutes.

Mix in the eggs and vanilla extract, scraping down the side of the bowl with a spatula, as necessary.

Add the dry ingredients and mix on low until just combined. Don’t over mix.

Scoop by the rounded tablespoon onto the prepared baking sheet, placing the dough balls about 2-inches apart.

Bake for 8 minutes. Open the oven and carefully slide out the pan. Gently press one marshmallow half in the center of each cookie. Try to work quickly. Push the pan back in the oven and bake for an additional minute so the marshmallows can get soft.

Remove the baking sheet from the oven and let the cookies cool on the pan for a few minutes, then transfer to a wire rack to cool completely. Garnish with finely chopped chocolate.