Chop the apples into little chunks and put them in a heavy bottomed pan. Grate on most of the zest of a lemon, leaving some aside, then add the juice of that lemon as well. Sprinkle on caster sugar and the white wine. Stir over the heat and allow it to very gently simmer for ten minute or so without ever coming to the boil.
Meanwhile, whisk together the mascarpone cheese, double cream, icing sugar and remaining lemon zest, until it is quite firm. Stir a couple of teaspoons of lemon curd in to the cream, and a couple of teaspoons of jam in to the apple mixture but leaving it splodgy and streaky.
Spoon the apple and jam mixture into serving dishes or sundae glasses and dollop the cream mixture on top. Decorate with more lemon zest, a dot of jam, or whatever you feel works. The syllabub can chill in the fridge until needed.