In a large mixing bowl, sprinkle the gelatin over the water and set aside.

In a medium mixing bowl, whisk the egg yolks and cornstarch until combined.

In a medium saucepan, combine the fruit, sugar, butter, and salt. Mash and mix before turning on the heat. Cook over medium heat until the mixture is simmering and the fruit is mostly broken down.

Remove the fruit from heat. While whisking, slowly stream about half of the fruit into the egg yolk mixture. Return the mixture back to the saucepan and cook until thickened.

Strain the curd through a strainer set over the bowl with the gelatin and stir until dissolved. Then set aside.

Adjust oven rack to middle position and preheat the oven to 350F degrees. Prepare cake pans.

Sift the cake flour and salt together.

Melt the butter in a microwave-safe bowl.

Mix eggs and sugar in a stand mixer until airy and pale.

Gently fold the sifted flour into the egg mixture.

Temper the butter with cake batter and fold gently.

Pour the batter into pans and bake until springy to the touch.

Cool the cakes in the pans for 10 minutes before inverting onto a wire rack.

Clean the mixing bowl and whisk attachment. Whip the heavy cream until soft peaks form.

Fold the whipped cream into the cooled berry curd.

Microwave the jam and lemon juice until hot and fluid.

Assemble the cake by spreading jam and mousse between the layers.

Refrigerate the cake for at least 4 hours.