In a heatproof mixing bowl, combine the vanilla sugar with the egg yolks.
Slowly add the icing sugar and the evaporated milk.
Now add the plum schnapps or rum or vodka.
Place the bowl over a pot of boiling water, making sure the water doesn't touch the bottom of the bowl. Stir continuously until the mixture gets thicker.
Fill the warm mixture into bottles.
Please note that the mixture will thicken further in the bottles, if too thick add either milk or schnapps/rum/vodka and shake the mixture in the bottle.