Method

• 1.
  Preheat oven to 180°C/160°C fan-forced. Grease base and sides of a 25cm x 38cm x 3cm-deep baking tray and line with baking paper.
• 2.
  To make the sponge, in a stand mixer fitted with the whisk attachment, whisk the egg whites, sugar and honey on high for 4-5 minutes, until firm peaks and sugar has dissolved. Add yolks and oil and whisk until combined. Sift over flour and stir by hand until just combined. Spoon batter into prepared tray and spread evenly. Bake for 10-12 minutes, until light golden and sponge springs back when pressed. Remove from oven and cool completely in pan on a wire rack, then stand in fridge for 15 minutes, or until sponge is firm and chilled. This gives you a nice clean edge when you cut out your base. Using base of a 20cm springform pan as a guide, cut out a circle of sponge for assembly. Set circle aside, and save offcuts for another use.
• 3.
  To make syrup, place sugar, vanilla and 100ml water in a medium saucepan and bring to the boil over high heat, stirring to dissolve sugar. Set aside to cool completely.
• 4.
  Stir through Grand Marnier, if using.
• 5.
  To make the glaze, bring berries, sugar and 200ml water to the boil in a large saucepan over high heat. Reduce heat to low and cook for 6-8 minutes, stirring frequently, until berries have broken down completely. Squeeze excess water from gelatine and stir into berry mixture until dissolved. Pass through a fine sieve into a jug, discarding solids. Cover and set aside to cool to body temperature.
• 6.
  To make the creme diplomat, bring milk and vanilla to the boil in a large saucepan over medium-high heat, then remove from heat. Meanwhile, whisk yolks, sugar, cornflour and a pinch of fine salt in a large heatproof bowl until pale and creamy. Gradually whisk in milk mixture until combined. Return mixture to pan and whisk constantly over medium heat until mixture boils and thickens. Remove from heat. Squeeze excess water from gelatine leaves and stir into custard until dissolved. Pass through a fine sieve into a bowl, cover and set aside to cool to room temperature. Whisk cream and extra sugar to medium-firm peaks. Gently fold in custard. Set aside.
• 7.
  To assemble, grease sides of a 20cm round springform pan and line sides with acetate. Place cut circle of sponge in base of pan. Drizzle generously with syrup.
• 8.
  Trim the halved strawberries so they're all a similar size (see notes) and arrange with cut sides against the inside of pan, pressing to ensure strawberries are firmly in place on base and against the acetate. Spoon diplomat until the pan is about two-thirds full and, using a small offset spatula, firmly push the cream up sides of pan, ensuring any gaps are filled between the strawberries.
• 9.
  Finish with remaining diplomat and level with a small offset spatula for a flat surface. Freeze for 30 minutes, until filling is firm and set enough to pour over the glaze.
• 10.
  Gently spoon glaze over the top so it spreads evenly. Chill for 1 hour, or until set.
• 11.
  Unmould cake and peel away acetate, then transfer cake to a serving platter. Decorate with extra strawberries.