First, make the jelly. Soak the gelatine leaves
in cold water until floppy, then drain. Strain
off the juice from the cherries into a jug – you
should have around 350-400ml. Put the juice
and the redcurrant jelly in a pan, stirring until
it boils and the redcurrant jelly has melted.
Take off the heat, cool for a few mins, then stir
in the gelatine until it dissolves. Pour into a
shallow pan or dish to cool, then chill until set.
For the custard, scrape the vanilla seeds
from the pod into a large bowl. Add the egg
yolks, 40g sugar and the flour, then whisk
until pale and creamy. Pour the cream into
a medium-size pan and bring just to the boil.
Gradually whisk the cream into the yolk mix.
Wipe out the pan, then return the mixture to
it. Cook slowly over a low heat, stirring with
a wooden spoon until thickened – take extra
care to stir well at the edges of the pan. Cool,
stirring every so often.
To assemble the trifle, slice the Swiss roll
into 8 pieces and arrange on the base and
around the inside of a large glass serving
bowl. Sprinkle with the sherry, if using.
Turn the jelly out onto a board and chop with
a sharp knife. Scatter the drained cherries
and chopped jelly on top of the Swiss roll,
then sprinkle over the crushed amaretti.
Pour the cooled custard over the biscuits,
then return to the fridge until cold (about 2
hrs). For the topping, whip the cream to soft
peaks with 1 tbsp sugar, then spoon or pipe
it over the custard. The trifle can be covered
and chilled for up to 2 days at this point.
To serve, sprinkle over the pistachios and
remaining amaretti. Push back the leaves of
the physalis and poke the fruit into the cream.