Jelly

Fill a large saucepan two-thirds full of water, sit a large bowl on top and bring water to the boil. In bowl, place 2 cups water, sugar and lemon juice and seeds, reduce heat and simmer, stirring, until sugar has dissolved. Add strawberries to bowl and cover tightly with a lid and simmer gently for 30-40 minutes until strawberries are tender and leached of colour. Stir occasionally.

Place a colander over a deep bowl and ladle or pour in strawberry mixture. Do not press strawberries (or jelly will not be clear). Leave for 10 minutes or until all juice has dripped through. Discard strawberries.

Lay gelatine leaves in strained liquid, swirling with a spoon or ladle until leaves are completely dissolved. Strain liquid through a fine strainer into a bowl or tray and refrigerate until set.

Jam

Combine mashed strawberries, sugar and lemon juice in a saucepan over medium heat and stir until sugar dissolves. Boil without stirring until jam reaches setting point (105°C-106°C on a sugar thermometer or until a small amount of mixture sets when placed on a chilled saucer). Remove from heat and set aside to cool to room temperature.

Sponge

Preheat oven to 180°C and grease a 20cm x 30cm x 4cm cake tray.

Line it with baking paper. Whisk egg yolks in a medium bowl with half the sugar until pale and thick. Using an electric mixer, whisk whites with a pinch of salt until firm peaks form, then gradually sprinkle in remaining sugar and beat until thick. Fold whites into yolk mixture, then sieve flour into egg mixture and drizzle in melted butter. Fold gently until well incorporated. Spoon mixture into cake tray and spread evenly. Bake for 20 minutes or until golden and dry in the centre when tested with a cake skewer. Invert onto a cake rack and allow to cool for 5-10 minutes.

Meanwhile, lay 2 sheets of plastic wrap, larger than the cake, onto workbench. Peel paper from cake, cut cake in half horizontally and gently lift each half onto plastic wrap with cut surface facing upwards. Spread each cake with jam, roll tightly in plastic wrap and leave to cool completely.

Mascarpone cream

Place cream and vanilla seeds in a saucepan and bring to the boil. Whisk half the sugar and egg yolks in a bowl, then pour cream mixture onto yolks and stir until smooth. Return mixture to saucepan and stir over a low heat until it is thick enough to coat back of a wooden spoon. Strain into a bowl, sit bowl in a large bowl of ice to cool, then refrigerate.

Whisk whole egg with remaining sugar with an electric mixer until thick and pale. Reduce speed and slowly add dollops of mascarpone and chilled custard, mixing well until smooth. Refrigerate until ready to use.

Assemble trifle

Dust hulled strawberries with icing sugar and mash slightly with a fork, then set aside.

Using a small serrated knife, cut jam rolls into thin slices and spread on a tray. Sprinkle with the sherry and any strawberry/icing sugar juice. In a large bowl or individual glasses, start with a layer of jam roll slices and alternate layers of mascarpone cream, jelly, slices of jam roll and macerated strawberries, finishing with a layer of mascarpone cream. Spread cream evenly with a spatula.

Half an hour before serving, heat a brulée iron and dust the top of trifle with a thin layer of caster sugar, then spray with a fine mist of water and slide brulée iron over surface to caramelise top. You can also use a kitchen blowtorch to caramelise top of trifle.