Preheat the oven to 350℉ and line two large baking sheets with parchment paper or silpat liners.
Add the softened butter and granulated sugar to the bowl of a stand mixer fitted with the paddle attachment. Beat until light and fluffy, at least 2 minutes.
Add the egg and vanilla and mix to combine.
In a small bowl, whisk together the flour, cocoa powder, and baking soda.
With the mixer on low speed, slowly add the dry ingredients to the creamed butter and sugar mixture. Mix just until no large lumps of flour remain.
Fold the chopped chocolate, mini marshmallows, and freeze dried marshmallows into the cookie dough, mixing just until they are evenly distributed.
Use a cookie scoop (or two spoons) to portion out tablespoon-sized balls. Place them on the parchment lined baking sheets, spacing at least 2 inches apart.
Bake the cookies for 12-14 minutes, or until the edges are set. Allow the cookies to cool completely on the pan before removing them to an airtight container or wire rack.
Notes
Cocoa Powder: I used Hershey’s unsweetened baking cocoa in this recipe, but you can substitute another brand of cocoa powder
Storage: Store any leftover cookies in an airtight container at room temperature for up to three days.
Substitutions & Variations
Substitute unsalted butter and ¼ teaspoon salt for the salted butter in this recipe
Use chocolate chips in place of the chopped baking chocolate
Instead of semi-sweet chocolate, try dark chocolate, milk chocolate or white chocolate
Use peppermint marshmallows to make mint hot cocoa cookies
For a stronger mint flavor, substitute peppermint extract for the vanilla extract