Make the custard: blend the sugar,
custard powder and cornflour with 1 tbsp
milk to make a runny paste. Beat in the
egg yolk. Pour the remaining milk into a
pan, scrape in the vanilla seeds, add the
pod, then allow to come just to the boil.
Stir this into the cornflour paste, then pour
into a clean pan. Cook over a medium
heat, stirring all the time, until thickened.
Remove from the heat, then stir in the
crème fraîche until smooth. Pour into
a bowl, cover the surface with cling film
to stop a skin forming, allow to cool,
then chill until completely cold.
Make the cake: heat oven to 180C/
fan 160C/gas 4. Lightly oil and line the base
of a 20cm round cake tin. Put the sugar
and eggs into a bowl. Whisk with electric
beaters for 5 mins until very thick, paler in
colour and the consistency of whipped
cream. Sift over the flour and quickly, but
lightly, fold it in. Spoon the mixture into
the tin and carefully level it, being careful
not to squash it. Bake for 25 mins until
risen, then remove and cool on a wire
rack. Peel off lining paper. Halve the cake
so you have a semi-circle. (The other half
can be frozen for another time.) Split the
semi-circle in half with a knife, then
sandwich back together with fruit spread.
Put the sugar and lime zest for the fruit
into a pan with 2 tbsp water. Bring slowly
to the boil until the sugar has dissolved,
then bubble for 1½-2 mins until syrupy.
Tip in the blueberries, then cook very
briefly, stirring once or twice only, just until
they start to burst and release their juices
(but still stay whole) and you get a purple
syrup. Set aside to cool.
The sponge and custard layers can be
built up to 2-3 hrs ahead of when you
want to serve. Cut the jammy sponge
into cubes, then place in the base of a
glass dish. Drizzle over the Marsala. Keep
about ¼ of the berries back for the top,
then spoon the rest over the sponge with
a little syrup. Discard the pod from the
custard, then pour it over the fruit.
Just before serving, beat the yogurt,
mascarpone and sugar together until
smooth and creamy. Pile onto the custard,
then drizzle over the reserved fruit and
syrup. Use a skewer to swirl some of the
juices through the creamy topping. Serve
straight away or the syrup discolours the
topping. This is best eaten the same day.