These could be:
- brandy butter
Cream, whether single, double, whipped, sour (!) or pouring is naturally gluten free, so unless you’re adding something very odd indeed, this should be fine.
Brandy butter should just be butter, sugar and brandy, though if you’re buying ready-made, do check the ingredients because as we know, manufacturers do tend to add flour to the oddest things. Brandy, incidentally, is gluten free (unless something is added post distillation). I always make ours, and I do it by eye (and taste), not by measure, so here are a couple of proper recipes for you. Interestingly, both use brown sugar where I use icing sugar (confectioners’ sugar) so I might try it with brown sugar this year:
Custard may be more risky. Traditionally, this is made using cornflour (see Mary Berry’s recipe for custard), and it is surprisingly easy to do, though I confess that when I make custard I omit the cream… If you’re buying custard, do check just in case. If you’re in the UK, then you can rely on Ambrosia and Bird’s.
Another option is to use a good thick yoghurt, probably Greek. And Greek yoghurt is available at 0% fat, if you’re trying to monitor such things over Christmas…