1. Slice the cake in half lengthways and sandwich together with the jam. Cut the cake into 3cm thick slices, then cut each slice into three so you get small rectangles of the sandwiched cake.
2. Use these to line the bottom of the trifle or glass dish. Pour over the sherry, and cover with the raspberries. Spoon the custard on top of the raspberries. Crush the amaretti biscuits and add to the top of the custard, pushing some of them in a little.
3. Whip the cream until it forms soft peaks, add to the top of the custard. Cover and chill for at least 4 hours, or overnight if you can. Scatter with flaked almonds to serve.