Line a 9x9-inch square pan with parchment paper or aluminum foil, leaving some overhang on the sides to easily lift the bars out later.

Lightly grease the parchment paper or foil with a bit of butter or non-stick spray.

In a saucepan, cook the butter, sugar, and cocoa powder over medium-low heat until the butter is melted, and the sugar is dissolved. Mix well.

In a small bowl, whisk a small amount of the butter mixture into the beaten egg.

Then add the egg mixture back into the butter mixture and continue cooking for 2-3 minutes whisking constantly. The mixture will thicken. When it coats a metal spoon or a thermometer reads 160°, remove from the heat.

Stir in the vanilla extract, graham cracker crumbs, and shredded coconut. Mix until combined.

Press the mixture firmly into the bottom of a 9x9-inch baking dish. Chill in the refrigerator for 30 minutes.

In a large bowl, using a handheld electric mixer, beat the softened butter until creamy.

Gradually add powdered sugar and custard powder, beating until smooth.

Add the half-and-half and continue to beat until the mixture is smooth, light and fluffy.

Spread the creamy custard filling mixture evenly over the chilled base layer. Return to the refrigerator for another 30 minutes.

In a microwave-safe bowl, melt chocolate chips and shortening in 30-second intervals, stirring until smooth.

Pour the melted chocolate over the custard layer and spread evenly.

Chill in the refrigerator until the chocolate layer is set, about 1 hour.

Once set, cut into squares using a sharp knife.