Line an 8x8 inch (20x20 cm) baking dish with parchment or foil, set aside.

In a medium saucepan over low heat, melt the butter with the cocoa powder and granulated sugar until smooth

Drizzle ½ cup of the butter mixture into a bowl with the egg, whisking constantly to temper the egg.

Pour the egg mixture back into the pot and turn the heat up to medium. Cook, whisking constantly until the mixture has thickened, about 4-5 minutes (or until it reaches 180°F/82°C).

Remove from heat, and stir in the graham crackers, coconut, and nuts until they are coated with the chocolate mixture.

Transfer to the prepared baking dish and once the mixture is cool enough to work with, press it down with buttered fingers into a smooth layer. Place the dish in the fridge to chill while you prepare the middle layer.

In a small bowl, whisk together the cream and the custard powder until smooth, set aside.

In a large bowl, add the powdered sugar to the butter in 2-3 smaller additions, beating well after each, until smooth and creamy.

Add the custard mixture and beat on high until light and fluffy.

Spread over the bottom layer, then return to the fridge to chill for 10 minutes.

In a microwave safe bowl, melt the chocolate chips and the butter in 30 second increments,stirring well after each, until the chips are melted and the mixture is smooth.

Spread the chocolate over the top of the squares, then return the dish to the fridge to chill for 30 minutes.

Slice the bars after 30 minutes (too long in the fridge will be difficult to slice). Store in the fridge. Best eaten at room temperature.