Prepare the Cookie Dough:

1. Cream the Butter and Sugar: In a large bowl, cream the softened butter and sugar together until light and fluffy.
2. Add the Egg and Cream Cheese: Beat in the egg and softened cream cheese until well combined.
3. Add Buttermilk, Vanilla, and Food Coloring: Mix in the buttermilk, vanilla extract, and red food coloring until smooth and fully incorporated.
4. Combine the Dry Ingredients: In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.
5. Mix Wet and Dry Ingredients: Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Be careful not to overmix.
6. Chill the Dough (Optional): For best results, refrigerate the dough for 15-30 minutes to make it easier to scoop and shape.

Bake the Cookies:

7. Preheat the Oven: Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
8. Shape the Cookies: Use a cookie scoop or tablespoon to portion out the dough, rolling it into balls. Place them on the prepared baking sheet, spacing them about 2 inches apart.
9. Bake: Bake the cookies for 10-12 minutes, or until the edges are golden and the centers are set but still soft.
10. Add Marshmallows: While the cookies are still warm, gently press one marshmallow into the center of each cookie.
11. Toast the Marshmallows: Return the cookies to the oven for an additional 1-2 minutes, or until the marshmallows are golden and slightly toasted.
12. Cool: Allow the cookies to cool on the baking sheet for 5 minutes before transferring them to a wire rack to cool completely.