600g (1lb 5oz) strawberries, hulled, plus a few extra to garnish 4 (or 7g/¼oz) gelatine leaves 250ml (9fl oz) Prosecco or Champagne 110g (3¾oz) caster sugar, plus extra for whipping 5 savoiardi sponges (lady-finger biscuits)
For the custard
50ml (2fl oz) semi-skimmed milk 570ml (1pt) double cream 1 vanilla pod, split lengthways 6 free-range egg yolks 40g (1½oz) caster sugar 6tsp cornflour
For the cream topping
200ml (7fl oz) double cream 300ml (10fl oz) Greek yoghurt Put 500g (1lb 1oz) of the strawberries in a heatproof bowl, cover with clingfilm and place over a pan of simmering water for about 30 minutes, until the juices run. Strain through a fine mesh sieve. You’ll need about 250ml (9fl oz) juice. Soak the gelatine in cold water until soft (about 2 minutes).
Gently heat the strawberry juice, Prosecco and 110g (3¾oz) sugar in a pan over a low heat until the sugar has dissolved. Squeeze the water from the softened gelatine leaves, add them to the pan and remove from the heat.
Place the last 100g (3½oz) of the strawberries into a 1.5ltr (2¾pt) dish. Layer the sponge fingers on top, pour the strawberry jelly over and put in the fridge to set.
For the custard, bring the milk, cream and vanilla pod to a simmer in a pan over a low heat. Remove the vanilla pod. Meanwhile, whisk the egg yolks, sugar and cornflour to a smooth paste. Slowly pour the warm cream mixture into the egg mixture, whisking continuously. Once two thirds of the cream is added, pour the resulting custard back into the pan with the remaining cream mixture and cook over a low heat, whisking constantly, until thick (5-8 minutes).
Pour the custard into a cold bowl and cover with a sheet of baking paper to stop a skin forming. Cool to room temperature, then chill. Pour over the jelly layer and return the trifle to the fridge.
Whisk the cream with 1tbsp sugar in a bowl until soft peaks form, then fold in the yoghurt. Pour this mixture onto the custard and garnish with chopped extra strawberries.