In a pan, gently heat the cranberries, sugar and orange zest and juice with 2 tbsp water for about 5 min until the berries are softened. Stir in wine, if using. Leave to cool to room temperature.
Meanwhile, heat a frying pan over a medium heat. Add nuts and toast until lightly coloured, but keep stirring and watching them as they burn easily. Tip into a bowl to cool.
Line the base of a 1.8 litre (31⁄4 pint) glass bowl with the trifle sponges, cutting them to fit if you need to. Spoon over the cooled cranberry mixture. Stir three quarters of the nuts into the custard, setting aside the rest for decoration. Spoon custard on to cranberry layer.
Whip cream and icing sugar together until it just holds soft peaks - it's vital not to whip it too much as the cream will turn buttery. Spread on top of the custard.
Cover and chill for at least 30 min to let the flavours mingle. To serve, grate chocolate directly on to the cream and sprinkle with the remaining nuts.
Get ahead: make to the end of step 3 up to 24 hours ahead. To use, complete the recipe just before serving.