Preheat the oven to 350F and line two 8x4-inch loaf pans with parchment.

In a large bowl, stir together the melted butter, cocoa, sugar and egg. Stir in the graham crumbs, coconut and nuts. Divide the mixture between the pans and press evenly into the bottom. (I find this easier with dampened hands.)

In the same bowl (no need to wash it) whisk together the flour, sugar, cocoa, baking soda and salt. In another bowl or measuring cup, stir together the water, oil, vinegar and vanilla. Add to the dry ingredients and whisk just until well blended. Divide between the pans, pouring over the Nanaimo bar base.

Bake for 50-60 minutes or until puffed, cracked and springy to the touch. Cool completely while you make the frosting.

In a large bowl, beat the butter until smooth, then add the custard powder, sugar and 1/4 cup of the cream and beat until you have a fluffy frosting, adding a bit more cream (or even a tablespoon of water) if needed. Once the cakes have cooled completely, spread with the frosting and put into the fridge until it firms up a bit.

To make the ganache, put the chocolate into a bowl, warm the cream to steaming on the stovetop or in the microwave and pour it over the chocolate, and let it sit for a few minutes. Whisk until well blended and smooth—it will appear broken at first, but then will turn darker and have a smoother, more even consistency. Set aside for 20-30 minutes, so that it firms a bit and isn’t so warm that it will melt the frosting, then pour or spread over each cake. Let sit until the ganache sets. Makes 2 cakes; serves about 16.