Line an 8x8 square pan with parchment paper, leaving enough of an overhang to pull the bars out of the pan when ready to serve.

Add the butter, sugar, and cocoa powder to a double boiler, heating over medium-low heat. Heat, whisking occasionally until the butter is completely melted and the ingredients are well combined.

Whisk in the beaten egg, whisking constantly to cook the egg and the mixture slightly thickens.

Remove from the heat and then stir in the graham cracker crumbs, finely chopped almonds, and the shredded coconut. Press the mixture into the prepared pan, forming a firm, even layer.

Using a hand mixer or stand mixer, cream together the butter, cream, custard powder, and powdered sugar.

Beat until light and fluffy then spread evenly over the bottom layer.

Add the chocolate to a microwave-safe bowl. Heat at 50% power for 1 minute then stir well to melt the chocolate. Continue to melt at 50% power for 20-second intervals, stirring after each time, until the chocolate is melted and smooth.

Once the chocolate is melted, stir in the butter. Then pour on top of the custard layer and use an offset spatula to spread in an even layer.

Refrigerate the bars for 15 minutes. Then remove from the refrigerator and use a sharp knife to score the chocolate into 16 slices, where they will be cut before serving. Scoring the chocolate will prevent the chocolate from cracking when you cut the chilled bars. Return the bars to the refrigerator and chill for at least 2 hours before serving.

Cut the bars into 16 squares before serving. Store leftovers in the refrigerator.