Using a food processor or nut chopper, grind the almonds up into coarse crumbs. Set up the double boiler and measure out all of the ingredients for the bottom layer.
In the top of the double boiler melt the butter. Whisk in the cocoa and sugar until smooth. Add the eggs and whisk continuously for about three minutes, until the mixture thickens and eventually becomes smooth. Remove from heat.
Add the graham crumbs, almonds and coconut to the chocolate and using a wooden spoon, mix until fully combined. Press into the bottom of an ungreased 9 x 13" baking dish and make layer as level as possible.
Sift the custard powder into the bowl of a stand mixer and add the butter and cream. Using the paddle attachment whip until the ingredients eventually fully combine, about 4 minutes on medium high speed. Whip in 1 cup confectioners sugar at a time, scraping the bowl in between each addition.
Using an icing spatula, spread the custard over the bottom layer in the baking dish. Spread as evenly as possible! Chill for 30 minutes. Just enough time to clean those dishes that piled up ;)
In a microwave safe bowl combine the chocolate chips and butter and melt on 50% power until fully melted. Pour over top of the custard and spread evenly. Refrigerate 30 more minutes. If you prefer you can use the double boiler. Just be cautious to keep it at a low temperature so you don't heat the chocolate too quickly - it will ruin the chocolate.
Cutting and Storage
Gently slide a knife through the top chocolate layer to form the bars, cleaning the knife often. I like to cut them so they are 3 x 8, resulting in 24 Nanaimo Bars. Look above at the process shots for photos. Refrigerate another 30 minutes to ensure the bars are firm enough.
Cut through the bars again, this time all the way through, and along the edges as well to pop the bars out of the baking dish. You can refrigerate these for 2 weeks, or freeze for 6 months.