Preheat oven to 350°F (175°C) and prepare a 9x9-inch baking pan by greasing it.

In a medium bowl, combine melted butter and granulated sugar and whisk until smooth and glossy.

Add eggs and vanilla extract, beating until fully combined and creamy.

In a separate bowl, whisk together cocoa powder, flour, baking powder, and salt, then stir into the wet mixture until just combined.

Fold in mini chocolate chips and pour the batter into the prepared baking pan.

Bake for 20-25 minutes until a toothpick comes out with a few moist crumbs.

Allow brownies to cool completely in the pan on a wire rack, about 30 minutes.

In a saucepan, combine heavy cream, butter, and vanilla over medium-low heat until melted. Stir in marshmallow fluff until smooth.

Pour marshmallow mixture over brownies and sprinkle shredded coconut on top.

Chill in the refrigerator for 30 minutes, then cut into squares and serve.