Peel and quarter the apples, cut out the core and cut into cubes. Steam the apples with the sugar, lemon zest and vanilla pod in the wine until soft. After the vanilla pod has been removed and the cornstarch mixed with a little water, let it boil again briefly. Fold in the beaten egg yolk and, if desired, season the cream with a dash of rum or calvados.
Let the cream cool and fold in the whipped cream.
Chill well and decorate with chocolate shavings if you like.