IckleBones - my go-to pudding is so easy, and everyone who has tried it, loves it - and you can make it in minutes. It is a lime or lemon cheesecake-type thingybob, but with no cheese.
Blitz up ginger biscuits and add softened butter. Line a flan tin with this, pressing it in firmly. I line up the sides as well - I think that makes it easier to get it out. Chill in the fridge (the biscuit base, not you - you get to chill on the couch with a glass of wine).
In a bowl combine one large tin of condensed milk and the same amount of double cream, and whisk. Add the juice and zest of a couple of lemons or 3-4 limes, to taste. The citrus juice will thicken the cream and condensed milk mixture. Pour it into the chilled biscuit base, smooth out, and chill again.
To serve - remove from flan dish. Serve with pouring cream, if you want. I once made a syrup with julienned strips of citrus peel, some of the juice, sugar and water, cooked slowly to a syrup and then chilled - that was very nice, but extra work that, frankly you don't need on Christmas day.
You could make this dessert on Christmas Eve, and it would keep fine in the fridge.