01 - Preheat oven to 350°F. Line an 8-inch square baking pan with parchment paper, leaving enough overhang on two sides to lift the brownies out later.
02 - In a large mixing bowl, whisk together the melted butter and granulated sugar until well combined. Add the eggs one at a time, beating after each addition, then stir in the vanilla extract until the mixture is smooth and glossy.
03 - Sift the cocoa powder, all-purpose flour, salt, and baking powder directly into the wet mixture. Fold gently with a spatula until just combined — do not overmix, as this will make the brownies tough.
04 - Pour the batter into the prepared pan and spread it into an even layer. Bake for 22 to 26 minutes, or until a toothpick inserted into the center comes out with moist crumbs clinging to it. Allow the brownies to cool completely in the pan on a wire rack.
05 - While the brownies cool, spread the shredded coconut in an even layer on a rimmed baking sheet. Toast in the 350°F oven for 5 to 7 minutes, stirring halfway through, until the coconut turns a deep golden color. Remove and set aside to cool.
06 - Place the unwrapped caramel candies and milk (or cream) in a microwave-safe bowl. Heat in 30-second intervals, stirring thoroughly after each burst, until the caramels are completely melted and the mixture is smooth and pourable.
07 - Fold the toasted coconut into the melted caramel until evenly coated. Spread this mixture in a thick, even layer over the completely cooled brownies, pressing gently to adhere.
08 - Combine the chopped semi-sweet chocolate and coconut oil (if using) in a microwave-safe bowl. Microwave in 20-second intervals, stirring between each, until the chocolate is fully melted and silky smooth.
09 - Drizzle the melted chocolate over the coconut-caramel layer in zigzag lines. Let the brownies set at room temperature, or refrigerate for 30 minutes until the chocolate firms up. Use the parchment overhang to lift the block from the pan, then cut into 16 squares with a sharp knife.