Preheat the oven to 350°F (175°C) and line a baking sheet with parchment paper.In a large bowl, cream the butter, brown sugar, and granulated sugar until light and fluffy.Add the eggs and vanilla extract, mixing until smooth and fully incorporated.In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.Gradually mix the dry ingredients into the wet mixture until a thick dough forms.Fold in the chocolate chips and mini marshmallows gently.Scoop tablespoon-sized portions of dough onto the baking sheet, leaving space between cookies.Bake the Hot Chocolate Cookies for 9–11 minutes until the edges are set and the centers remain soft.Allow the cookies to cool on the baking sheet for a few minutes before transferring to a wire rack.