For the caramelised apples, place 70g/2½oz butter and all the sugar into a frying pan and heat gently until melted together and combined.
Add the apples and a squeeze of lemon juice, vanilla and lemon zest and cook gently for five minutes, or until the apples are beginning to turn golden. Set aside and keep warm.
Melt the remaining 15g/½oz of butter in a clean small frying pan, add the slice of bread and fry for two minutes on each side. Dust with icing sugar and fry for another minute on each side.
For the sabayon, place the egg yolks, caster sugar, brandy and water into a small heatproof bowl that fits snugly over a pan of gently simmering water. Whisk continuously until thickened. Add more water if the mixture is too thick. It should be the consistency of double cream.
To serve, place the sugared toast onto the base of a plate and pile the apples on top. Spoon on a dollop of ice cream and pour over the sabayon.
