Preheat your oven to 350°F (175°C) and prepare an 8x8-inch baking pan by greasing it lightly or lining it with parchment paper.

In a medium mixing bowl, combine melted unsalted butter and granulated sugar, whisking until smooth and creamy. Add eggs one by one, whisking until fully incorporated, and then stir in vanilla extract.

Sift in cocoa powder, all-purpose flour, baking powder, and a pinch of salt into the bowl. Fold the dry ingredients into the wet until just combined, leaving some lumps.

Fold in mini chocolate chips until evenly distributed throughout the batter.

Pour the brownie batter into the prepared baking pan, spreading evenly. Bake for 20-25 minutes until a toothpick comes out with a few moist crumbs.

Remove from the oven and allow to cool completely in the pan for at least 30 minutes.

In a saucepan over low heat, combine heavy cream, butter, and vanilla, stirring until warmed. Add marshmallow fluff and stir until smooth and creamy, about 3-4 minutes.

Spread the warm marshmallow mixture over the cooled brownies and immediately sprinkle shredded coconut on top, gently pressing down.

Refrigerate the brownies for 30 minutes to set the topping.

After chilling, lift the brownies out using parchment paper and cut into squares, wiping the knife for clean edges.