Preheat your oven to 350°F (180°C).

Line a baking sheet with parchment paper.

In a mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until light and fluffy.

Beat in the eggs one at a time, followed by the vanilla extract.

In a separate bowl, combine the flour, cocoa powder, baking soda, and salt.

Gradually add the dry mixture to the wet ingredients, mixing until just combined.

Fold in the chocolate chips and mini marshmallows.

Using a cookie scoop or spoon, drop dough onto the prepared baking sheet.

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

Let the cookies cool on the baking sheet for a few minutes before transferring them to a wire rack.