Start by melting the white chocolate. In a small saucepan, heat up the heavy cream until it starts to steam. Then pour it over the white chocolate and stir it together with a rubber spatula. Add the vanilla bean paste and with a hand blender, blend the mixture until smooth. Cover it with some cling film, so it touches the surface of the cream, and place it in the fridge for 5-6 hours until completely cold or preferably overnight.

Add the strawberries, blueberries, granulated sugar and lemon juice to a saucepan and heat it up until the berries starts to break down, and the liquid has come to a bubble. Once bubbling, turn it down to a simmer. Stir occasionally and with a rubber spatula mash down the berries.

Let it simmer for 8 minutes or until the jam has thickened. Then in a cup mix together cornstarch and water and pour it into the jam. Continuously stir it around for 1 minute while it thickens. Take it off the heat and using a hand blender, blend it until smooth.

Pour the jam into a shallow bowl, covered with plastic wrap, to let it cool down faster, and place it in the fridge. Let it cool down until cold.

Preheat the oven to 175ºC /350ºF conventional oven. Prepare 2x 30x40 cm / 12x 16 inch sheet pans with parchment paper. Do NOT grease the sides of the pans as the batter needs to cling to the sides as it rises, which helps the sponge achieve maximum height and a light texture.

Separate the egg whites and egg yolks into two clean bowls. Add the egg whites and white vinegar to the bowl of a stand mixer, using the whisk attachment, or a hand mixer, and beat the egg whites until foamy, on medium speed, then in a slow steady stream pour in the sugar while the egg whites continue to whisk. Continue whisking at high speed until stiff peaks.

Stir the egg yolks together and add them to the meringue together with the vanilla bean paste. Mix it together at the lowest speed until just combined.

Sift the all-purpose flour and salt and add it to the meringue. Mix it together at the lowest speed until just combined, it’s important not to over mix the batter.

Then finally heat up the heavy cream until it starts to steam and pour it into the batter and again mix until just combined.

Give the batter a final mix with a rubber spatula to make sure everything is combined.

Divide the cake batter into the pans and bake them for 11-12 minutes.

Once baked, immediately trace a thin knife along the edge of the pan and flip it upside down, onto a cooling rack. Flip it back around so it faces the right way up.

Whip the ganache until medium peaks. Using a serrated knife, cut the two sponge into two so each layer is 30x20 cm. Add the first sponge layer onto your serving plate and add 2-3 tbsp of the jam and even it out. Leave 1-2 cm around the edges so the jam doesn't spill.

Add ⅔ of the whipped white chocolate ganache to a piping bag and cut the tip off. Pip a boarder and pip as well on top of the jam, using a ⅓ of the cream in the piping bag. Using a offset spatula, even it out.

Continue the same process 3 more times. Scrape down the side and add the remaining whipped white chocolate ganache that was left in the bowl. Spread it over the cake and even it out. Place it in the fridge to set.

Once ready to serve, decorate it with lots of mixed berries. This cake is great to make a day ahead of serving it as it stays soft in the fridge.