Preheat your oven to 180 degrees. Line and grease a 18cm square tin
Sift the flour three times and put aside.
Put the eggs, caster sugar and brown sugar in a bowl and beat together for 8-10 minutes with an electric mixer until mixture is pale and thick and has tripled in size
Sift flour over the mixture and fold together gently, then fold in the butter.
Using a spoon, put mixture into tin, and bake for 25 minutes.
While cake is baking, make caramel sauce by stirring together brown sugar and cream in a small saucepan over medium heat until the sugar has dissolved. Increase the heat and simmer for around 8 minutes or until the sauce has thickened. Let the sauce cool slightly in the saucepan, before transferring to another container and place in the fridge for 20 minutes to cool completely
Cool cake in tin for 5 minutes and then turn onto a cake cooling rack - leave until completely cooled before slicing cake in half
Beat together cream, drop of vanilla essence and 2 tablespoons of icing sugar until cream is whipped
Spread half of cake with cream, cover with half of the banana slices, and half of the caramel sauce
Carefully place top layer onto the cake and repeat. Place in the fridge until ready to serve.