Preheat oven to 325° F. Line two cookie sheets with parchment paper or a silicone baking mat .

In a medium mixing bowl, whisk together the flour, cocoa powder, baking soda, and salt until well combined.

In a small heatproof (glass) bowl, melt the chocolate chips with the butter in the microwave in 30-second increments, stirring between each.

Transfer the chocolate and butter mixture to a large bowl, and add the sugar, eggs, and vanilla. Mix with a sturdy fork until well combined. Slowly mix in the flour mixture until just combined. Fold in the mini chocolate chips, the 1 cup of marshmallows, and the chopped pecans.

Refrigerate the dough for 30 minutes to an hour, until slightly firm. Using a 1 ½ tablespoon cookie scoop , make balls of dough and place them on the lined cookie sheet, leaving a couple of inches of space between each one. Stick two to 3 mini marshmallows in each raw cookie, pressing down lightly.

Bake about 15 minutes, or until the cookies are slightly puffy in the center but crispy around the edges, and the marshmallows have turned golden and melty. Carefully pull the cookies out of the oven, and let cool on the baking sheet for a few minutes to harden. Transfer to wire rack and let cool completely. Devour.