Line a deep, preferably glass, bowl tightly with ladyfingers, filling the gaps too. Pour over the Sherry.
Coarsely crush the ginger biscuits with a rolling pin, sprinkle over the ladyfingers. Spoon over the jam. Ideally let it rest for 1-2 hours in the refrigerator.
Grate the zest of the mandarins, set aside. Remove the white membrane, then cut the flesh into small wedges.
Layer the mandarin slices on top of the jam then spoon over the custard.
Whip the cream with the liqueur and zest until light and creamy. Spoon this on top of the custard.
Rest for at least 2-4 hours in the refrigerator - overnight would be even better!
Sprinkle with pomegranate seeds and some toasted almond flakes before serving.