2. Soak the gelatine in cold water to soften it. Using a hand blender, blend the cooked fruit (use a potato masher), then strain through a sieve into a large bowl and push through the pulp – discard the seeds and skins. Squeeze any excess water from the gelatine, then add to the hot fruit syrup and stir to dissolve. Cool, then place in the fridge to chill until almost set.
3. Make the custard according to pack instructions with the custard powder, milk and 50g sugar to create a thick custard. Cover the surface with baking paper while it cools.
4. Place the cubed cake into a trifle bowl, spoon over the juice and berries that you previously set to one side, then add the sherry. Pour over a thick layer of custard, pushing it against the side of the dish to seal in the cake below. Leave to cool.
5. When the custard is cold and set, spoon the jelly over the custard and chill until ready to complete.
6. Whip the cream with the vanilla and icing sugar until just holding its shape, then spoon round the bowl over the set jelly. Scatter with the crushed biscuits and chill until ready to serve.