Line a 8-inch by 8-inch square baking dish or pan with either plastic wrap or aluminum foil. The original recipe does not call for lining the pan, but believe me, this makes for a must neater and easier removal of the finished bars.
Place the beaten egg in a small bowl; set aside.
In a heavy saucepan over low heat, melt the butter, sugar, and cocoa. Whisk a small amount of the hot melted mixture into the egg. Return the egg mixture to the pan, whisking constantly. Cook and stir until mixture reaches 160 degrees F. on your cooking thermometer and begins to thicken. Remove from heat and stir in the graham cracker crumbs, almond or pecans, and coconut.
Press the cracker mixture firmly into the prepared baking dish or pan. Set aside.
In a large bowl of your electric mixer, cream together the butter, cream, custard powder, and powdered sugar until well blended. Spread over the Crust Base. Refrigerate at least 15 minutes or until set.
In a large saucepan over low heat, melt together the chocolate and butter. Remove from heat and pour the chocolate mixture over the chilled Custard Filling. Refrigerator at least 1 hour or until set.
Nanaimo Bars may be stored in the refrigerator, covered up to 1 month.
* Bird's Custard Powder is widely available in the UK and Canada. However, it is harder to find in other areas of the world. If you are unable to find it, you could substitute instant vanilla pudding or corn starch.
Nanaimo Bar Recipe: https://whatscookingamerica.net/Cookie/NanaimoBars.htm