Line a 9x9” baking dish with tin foil or parchment paper.
For the base layer, melt butter in a double boiler over low heat. Mix in sugar, cocoa powder, and salt and mix until combined.
Slowly add in the beaten egg to the mixture, whisking constantly to prevent the egg from cooking. Return to double boiler and cook for an additional minute or two for slight thickening. Your mixture should resemble a fudge-like consistency when ready.
Add graham cracker crumbs, shredded coconut, and pecans. Mix until hydrated.
Add to the prepared baking dish and spread in an even layer. Store in the fridge until ready for the second layer.
Add butter, custard powder, vanilla, powdered sugar, and heavy cream to the mixer with a paddle attachment. Mix until light and fluffy. If too thick, add a small amount of cream until a spreadable consistency has been reached.
Spread mixture on top of the first layer. Store in the freezer while chocolate ganache is made.
Add semi-sweet chocolate and cream to a heatproof bowl and melt over a double boiler. Once smooth, remove the pan from the freezer and pour melted chocolate over top, spread quickly and evenly.
Return the pan to the refrigerator for 15 minutes. Remove and score chocolate with a sharp knife.
Return to fridge to set further. When the chocolate has completely set, remove from fridge, and cut squares.
Serve.