Strawberry Jam:
Prepare the strawberry jam in advance. In a small saucepan, add the strawberries, sugar, and lemon juice. Bring to a simmer, stirring occasionally. Simmer for 15-20 minutes until thickened. Remove from heat and let cool completely before using.
Vanilla Lemon Sponge: 2. Preheat the oven to 350°F (180°C). Grease and line two 12×16 inch (30x40cm) baking sheets with parchment paper. 3. Separate the egg whites from the yolks. In a large bowl, mix the egg yolks with ¾ cup (150g) sugar until creamy. Add vanilla extract and lemon zest, mixing to combine. 4. Gradually sift the flour, baking powder, and salt into the yolk mixture, gently folding to incorporate. 5. In a separate bowl, whip the egg whites until foamy. Gradually add the remaining ¼ cup (50g) sugar and whip until stiff peaks form. 6. Carefully fold the whipped egg whites into the yolk mixture in batches, ensuring not to deflate the batter. 7. Divide the batter evenly between the prepared baking sheets and spread it out evenly. Bake for 10-12 minutes, or until a toothpick inserted into the center comes out clean. 8. Dust the baked sponge with powdered sugar, flip it onto another sheet of parchment paper, and peel off the original baking paper. Let the sponge cool completely.
Mascarpone Lemon Frosting: 9. In a large bowl, beat the Mascarpone cheese until smooth. Add powdered sugar, vanilla extract, and lemon zest, mixing until incorporated. 10. Gradually add the chilled whipping cream and continue mixing until stiff peaks form.
Assembly: 11. Once the sponge cakes have cooled, cut each one in half to create four layers. 12. Place a small amount of frosting on the serving platter to hold the first sponge layer in place. Add the first layer of sponge and evenly spread a layer of strawberry jam. 13. Spread ⅓ of the mascarpone frosting on top of the jam. Repeat with the remaining sponge layers, alternating between strawberry jam and mascarpone frosting. 14. Refrigerate the assembled cake for at least 1 hour or overnight for best results. 15. Once chilled, trim the edges of the cake to create clean sides and cut into 12 rectangular slices. 16. Using a 6B piping tip, pipe whipped cream on top of each slice and decorate with fresh strawberry halves.