Freezing home made custard

[Pennies]

I want to freeze this in ice cube trays so I can give DD individual portions. How do I do this without it forming a skin?

Just sprinkle a little icing sugar over the surface of the custard

Frozen custard is just icecream though isnt it? Try finding out from a recipe for making custard based icecream - freeze it in one big batch and then scoop out a little portion as and when.