Preheat your oven to 350°F (175°C) and line two cookie sheets with parchment paper.

In a medium bowl, sift together 1 cup of all-purpose flour, 1/2 cup of cocoa powder, 1/2 teaspoon of baking soda, 1/4 teaspoon of baking powder, and 1/4 teaspoon of salt. Set aside.

In a large bowl, combine 1/2 cup of melted unsalted butter, 1/2 cup of packed brown sugar, and 1/4 cup of white sugar. Stir in 1 teaspoon of vanilla extract, 1 egg, and 1 egg yolk until smooth.

Fold the sifted dry ingredients into the wet mixture until just incorporated.

Allow the dough to rest for about 10 minutes on the counter.

Use a cookie scoop to portion out the dough, roll into balls, and coat in white granulated sugar.

Place 12 dough balls on each lined cookie sheet. Cut marshmallows in half and set aside.

Bake the cookies for about 6 minutes, until they are soft and slightly puffed.

Quickly place marshmallow halves on top of each cookie and bake for an additional 2-3 minutes.

Let the cookies cool for about 2 minutes and top each with a Hershey's Kiss before transferring to a wire rack.