Now that we have our ingredients, let’s dive into the process of creating this delightful cake. Follow these steps, and you’ll be enjoying a slice in no time:

1. Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking pan and set aside.
2. In a large bowl, whisk together the flour, granulated sugar, brown sugar, salt, baking soda, and cocoa powder.
3. In a saucepan over medium heat, combine the butter, Coca Cola, and cocoa powder. Stir until the butter melts completely and the mixture is smooth.
4. Pour the hot Coca Cola mixture over the dry ingredients and stir until just combined.
5. Add the buttermilk, eggs, and vanilla extract to the batter, mixing until smooth.
6. Fold in the mini marshmallows and chocolate chips, ensuring they’re evenly distributed throughout the batter.
7. Pour the batter into the prepared baking pan, smoothing the top with a spatula.
8. Bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
9. Allow the cake to cool in the pan on a wire rack before cutting into squares.