step 1
In a bowl mix the butter with the caster sugar until smooth.
step 2
On top of this cream add the hot chocolate powder and cocoa, then mix everything together.
step 3
In a separate bowl mix the dried powder milk and the water, then add the cocoa mixture.
step 4
Pour the cream in the pastry case and put it in the fridge over night.
step 5
Cut the cake in slices and it's ready to serve.