Prepare the Base Layer: In a medium bowl, cream together the softened butter and granulated sugar until light and fluffy. Beat in the egg.
Mix in the graham cracker crumbs, cocoa powder, and shredded coconut until well combined.
Press the mixture firmly into the bottom of a greased 8x8-inch baking pan to form an even layer. Set aside.
Make the Custard Layer: In another bowl, beat together the softened butter, powdered sugar, custard powder, milk, and vanilla extract until smooth and creamy.
Spread the custard mixture evenly over the base layer, smoothing it out with a spatula. Refrigerate for 30 minutes to set.
Prepare the Chocolate Topping: In a small saucepan over low heat, melt the chopped chocolate and butter together, stirring until smooth and melted.
Pour the melted chocolate over the custard layer, spreading it evenly.
Refrigerate again for 1-2 hours or until the chocolate is fully set.
Once set, cut into squares or bars and serve.
Notes
For best results, refrigerate after each layer to ensure proper setting.