Begin by whisking together 1 ½ cups of all-purpose flour, ½ cup of unsweetened cocoa powder, ½ teaspoon of baking soda, and ¼ teaspoon of salt in a medium bowl.

In a large mixing bowl, beat together ½ cup of softened real butter, ½ cup of granulated sugar, and ½ cup of brown sugar until the mixture becomes light and fluffy.

Add in 1 large egg and 1 teaspoon of vanilla extract, mixing until just combined.

Gradually mix the dry ingredient mixture into the wet ingredients in three separate additions while gently folding them together.

Fold in 1 cup of mini marshmallows and ½ cup of chocolate chips until evenly distributed.

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

Using a tablespoon, scoop out the dough and drop it onto the prepared baking sheet, spacing the balls about 2 inches apart.

Bake for 10-12 minutes, until the edges are set but the centers are slightly underdone.

Remove the cookies from the oven and let them cool on the baking sheet for about 5 minutes before transferring to a wire rack.