Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.

In a stand mixer, cream together one cup of softened butter and one cup of sugar until light and fluffy.

Add two large eggs, one at a time, mixing thoroughly after each addition.

In a separate bowl, sift together two cups of all-purpose flour, half a cup of cocoa powder, one teaspoon of baking soda, and half a teaspoon of salt. Gradually add to the wet ingredients.

Fold in one cup of semi-sweet chocolate chunks and one cup of mini marshmallows using a spatula.

Scoop the dough onto the prepared baking sheet, spacing them about two inches apart.

Bake for 10-12 minutes, until edges are set but centers look soft.

Allow to cool on the baking sheet for 5 minutes before transferring to a wire rack.

Let the cookies cool completely for about 15 minutes.