Prepare the Pan & Egg Mixture
Grease an 8x8 inch pan.
In a small bowl, stir together the liquid egg substitute and vanilla extract.
Set aside.
Make the Bottom Layer
Create a double boiler by placing a metal bowl over a saucepan filled halfway with barely simmering water. Melt 1/2 cup (480 ml) of butter in the bowl.
Stir in the cocoa powder and granulated sugar until smooth.
Remove from the heat.
Quickly whisk in the egg and vanilla mixture until combined.
Fold in the graham cracker crumbs, coconut, and chopped pecans until thoroughly mixed. Press the mixture firmly and evenly into the bottom of the prepared pan.
Refrigerate while you prepare the next layer.
Make the Middle Layer
In a large bowl, use a wooden spoon or electric mixer to cream the 2 tablespoons (30 ml / 1 fl oz) of butter with the custard powder until smooth.
Gradually add the powdered sugar and half-and-half, mixing until you have a smooth, creamy icing.
Spread the icing evenly over the chilled bottom layer.
Freeze for at least 2 hours to set completely.
Make the Top Layer & Finish
Using the double boiler method again, melt the remaining 1/2 cup (480 ml) of butter and the semisweet chocolate together, stirring until smooth.
Remove from heat and let it cool slightly.
Once it's cool but still pourable, spread it evenly over the frozen middle layer.
Return the pan to the freezer for at least 2 more hours, or until the chocolate is firm.
Cut into 20 bars and serve.
