In a large pot, melt the butter, sugar and cocoa together until it's smooth.
Quickly beat in the egg, making sure there are no lumps.
Add in the graham crumbs, coconut and walnuts. Firmly press into the bottom of an un-greased 9x9 pan. Chill in the refrigerator while you get the middle layer ready.
Get your middle ingredients together. Custard powder should readily be available in any store and is what gives the middle layer the yellow color.
Cream the icing, butter, milk and custard powder together with a mixer, then spread onto the bottom layer.
Melt the cup of chocolate chips and 2 tbsp of butter together.
Spread the chocolate on top evenly, then cool in the fridge for a couple hours. The nanaimo bars are best chilled, they hold together the best, since the middle layer is well, butter!