Preheat oven to 180 degrees C (350 degrees F). Line the bottom of a 18-20 cm baking pan with a circle of parchment paper and then grease well the pan.
In a large bowl beat egg yolks with sugar and vanilla extract on high speed of the mixer. When the mixture becomes thick and creamy, add orange juice and orange zest and stir. Gently fold in flour and salt just until combined.
In a separate bowl whip the egg whites until thick and fluffy. Carefully fold the egg whites into the yolk mixture.
Pour the batter into the greased pan. Bake for about 40-45 minutes or until a wooden skewer inserted in the centre is clean. Let the cake stay 10 minutes in the pan before removing it.
Allow the cake to cool until room temperature (preferably on a wire rack) before assembling it.
In a mixing bowl whip 150 ml heavy cream (cooled in the fridge for at least 6-8 hours).
In a heatproof bowl combine white chocolate and the remaining 50 ml heavy cream. Place the bowl over a pan of simmering water. Stir until the chocolate is completely melted. Remove from heat and add the orange zest. Stir until absorbed in the chocolate.
Gradually fold the chocolate mixture into the whipped cream until both parts are well combined.
Leave the mousse in the fridge for an hour before assembling the cake.
Peach Buttercream Frosting:
Combine peaches and sugar in a small saucepan over medium heat and bring to boil. Let the mixture simmer for 10-15 minutes. When it starts thickening remove from heat and set aside to cool.
In a large mixing bowl combine butter, vanilla and powdered sugar and beat until soft and fluffy. Gradually add the peach mixture (cooled until room temperature) and continue beating until well combined.
Assemble the cake:
Cut the cake base horizontally in 3 equal layers.
Place one layer on a serving plate. Sprinkle it with 1 tbs orange juice. Evenly spread half of the orange mousse on top. Cover with a second layer, sprinkle orange juice and spread the remaining orange mousse on top. Place the third layer, again sprinkled with juice. Spread the Peach Buttercream Frosting all around the top and the sides of the cake. Transfer the cake to the fridge for few hours.
Before serving make a caramelised butter: in a small saucepan over medium heat combine brown sugar, butter and 2 tbs orange juice. Whisk until the butter and the sugar are completely melted.
Let the caramel cool for 2-3 minutes and spoon it on top of the cake, around the sides so that it starts dripping down. Decorate with fresh fruits on top.