Into a small dish, add the powdered gelatin and cold water. Stir it together and set it aside to bloom for 10 minutes.

Add the cream and vanilla into a small saucepan, and place it over a medium heat, stirring occasionally.

While it heats, scoop the bloomed gelatin into a tall measuring jug, along with the mascarpone and white chocolate.

Once the cream is steaming, pour it into the jug and allow the mixture to sit for 2 minutes. Then, using a hand blender, blend until smooth. Cover the surface with clingfilm and refrigerate for a minimum of 6 hours.

Pre-heat the oven to 180C/355 (non-fan assisted or 165C/330F fan assisted). Lightly grease a 39 x 27 x 2cm baking tray and then line it with parchment paper.

Into the bowl of a stand mixer, add the egg yolks, 45g caster sugar, vanilla and lemon zest. Whisk on a medium high speed, until it reaches a thick and pale in consistency.

Into the bowl of a stand mixer, add the egg whites, and whisk on a medium low speed until frothy.

Increase the speed to medium and add the remaining 70g of sugar, 1 tablespoon at a time.

Once you have added all of the sugar, keep whisking, until you have a medium stiff peak.

In three parts, fold the meringue gently through the egg yolk mixture, until there are no streaks of meringue.

Sift in the flour and salt, and fold this through.

Pour in the oil and milk and fold this through.

Pour the batter into the lined tin and bake for 22 minutes, or until it is a really even golden brown colour and springs back slightly when you touch it.

Remove the tray from the oven, and immediately with the parchment paper, slide the sponge off the tray, and onto a wire cooling rack. Cool for 30 minutes at room temperature.

Take the cooled sponge and flip it over onto a larger sheet of parchment paper. Peel off the parchment on the sponge.

On the right hand, short edge, use a serrated knife to trim it at a 45 degree angle.

On the left hand, short edge, trim off the very end where the sponge is a bit shaggy. Then score three vertical lines.

Add a few tablespoons of jam to the sponge, and spread it out, creating an even layer.

Remove the vanilla cream from the fridge and in the bowl of a stand mixer, whisk it on a medium speed until it holds a medium peak.

Add the mixture into a piping bag, and pipe even lines across the sponge.

Use a warm palette knife to spread this evenly across the sponge.

Starting from the left hand edge, fold the sponge on itself, trying to ensure you get a really tight fold.

Wrap the parchment paper around the sponge, ensuring the 'tail'/seam that we created is on the underside.

At this point, if you have a pipe, slide the sponge (wrapped in the parchment) into the pipe.

Now, in order to keep it in that shape, we need to get it very cold, by refrigerating it for 4-6 hours or freezing it for about 45-60 minutes.

Once it has set, you can decorate it as you wish, then use a warm serrated knife to slice it.