If using frozen raspberries, set them out to thaw in advance.
If making your own custard sauce, either from scratch or a powder, do it now and set aside.
Whip up the cream, set aside.
Put the amaretti in the bottom of a large, nice-looking bowl (glass, ideally.) Don't crush or break them up.
Glug a generous amount of sherry on top of them.
If using fresh raspberries, set a few aside for a garnish and coarsely crush the rest. If using frozen, pick out a handful of the most intact looking ones and set aside. Mix the "non-set aside" raspberries with some icing sugar to make it as sweet as you think it needs to be, then spread the strawberry mixture all over the amaretti.
Spoon the custard over. Top with a healthy layer of whipped cream, garnish with the reserved raspberries, and chill before serving.