This is my mother’s recipe. It has been altered to be less sweet & greasy.
You need a spiral flat bottomed whisk (preferably) or a roux whisk.
Chop 1 cup pecans, add 1 1/4 cup each of fine unsweetened coconut and graham wafer crumbs. Set aside. In separate bowl whisk 1 egg until well mixed, no bits of white showing. Set aside.
In stove-top type pot:
Melt 1/3 cup butter on low heat.
Add 1/2 cup sugar, stir with flat whisk when sugar is mixed in
Add 2/3 cup cocoa.
Heat and stir with whisk until smooth, no granules of sugar.
If too dry add a little cream - maybe 1 tablespoon.
Remove from heat and add 1 teaspoon vanilla. Stir and then add the whisked egg slowly, whisking continuously.
If you add it too fast and don't whisk, you get bits of egg cooking due to the heat of the mixture.
Add the graham wafer crumbs, pecans and coconut and stir well with fork.
If it seems runny add more graham crumbs, 1/4 cup at a time until it has a good texture for pressing into the bottom of the cake pan—not dry, not runny.
Press with hands to cake pan bottom, making even as possible.
2 tablespoons of real butter, softened
2 tablespoons of evaporated milk or half and half cream
2 heaping tablespoons Birds vanilla custard powder
3/4 teaspoon vanilla
1 1/2 cups icing sugar, add another 1/4–1/2 at end as necessary to make it spreadable.
Spread over first layer and put in fridge to chill.
Unwrap and put into microwave proof casserole bowl. Don't allow the squares to touch liquid
5 squares unsweetened chocolate (from the baking section—they come in boxes of 8)
5 squares semisweet or dark chocolate
Microwave on power level 4 for approx 5 minutes until blocks can be stirred (by dry fork or knife with no liquid)
Immediately spread on cake. After a few minutes, chill in fridge. After chilling for maybe 30 minutes, take out pan to cut the pieces before the chocolate gets too hard. Note that liquid causes chocolate to seize up and it goes hard and can't be spread. thus the need to handle it with care.
Good luck, it's a lot of work but worth it.