Years ago I had to cobble together a trifle from whatever I had in, but it was so popular I've had to make it every year since - and it's super easy.
You need two Jamaican ginger cakes, rum, custard, cream, tinned mandarins, chocolate flake.
Chop up a ginger cake, put it at the bottom of the (huge) trifle dish, douse liberally with rum, add some strained mandarin segments.
Whack on a good layer of custard, then do a second cake/rum/mandarin layer. Then another custard layer.
Finish with cream - preferably boozy, orange flavoured cream - and scatter broken up chocolate flake on the top.
It works with regular or chocolate custard.