1. Preheat oven to 350°F (175°C) and line a 9×9-inch pan with parchment paper.

2. In a bowl, whisk melted butter and sugar until smooth, then add eggs one at a time and stir in vanilla extract.

3. In another bowl, combine flour, baking powder, salt, hot cocoa mix, and cocoa powder.

4. Gently fold dry ingredients into the wet mixture until just combined, then stir in chocolate chips.

5. Spread batter evenly in prepared pan and bake for 23–27 minutes until edges are set and center is slightly soft.

6. Remove brownies from oven and let rest for 5 minutes before topping.

7. Drop spoonfuls of marshmallow cream across the warm brownies and swirl with a knife or skewer.

8. Allow brownies to cool completely, then lift from pan and cut into squares.

9. Store in an airtight container at room temperature for up to 3 days.