Check the Butter Sponge Cake Post at basic recipes. When you're able to touch the cake and not getting burnt, wrap it with cling film and store in the fridge until you need it.
In a small saucepan, bring water and sugar to boil.
Take it off the heat and let it cool.
When at room temperature, add coconut liqueur, stir, pour into a jar and store it in the fridge.
Set aside a little bit of milk in a mug.
In a pot add the remaining milk, sugar and chocolate flavor milk powder and whisk well. Get it over medium-heat and stir from time to time.
When milk gets really hot (without boiling), add cornstarch to the mug with milk and whisk it very well (I used a fork). Then add this cornstarch mixture to the milk pot and keep stirring.
After you see the first bubble, reduce the heat to low and keep stirring for one more minute.
Take it off the heat and add chocolate in pieces, stir again.
Pour into a heat-prof bowl and cover with cling film. Let it cool completely and store it in the fridge.
Cut the cake into 8 or 10 pieces.
With a pastry brush, soak every side of the sponge cake pieces with coconut syrup.
Wisk chocolate cream to end up with a smooth and homogeneous cream.
Spread, over all sides of the cake, chocolate cream and then cover them with grated coconut. With help of an offset spatula, lay it on a plate ready to serve or on a tin sheet and wrap it. Store in the fridge for up to 4 days.
*If you're giving these cakes to kids, you can change the coconut liqueur for some drops of pure coconut extract or just keep it plain.