Preheat the oven to 180˚C/160˚C fan/gas mark 4. Grease and line a 20cm loose-bottomed or spring-form cake tin.
To make the sponge, first whisk the egg yolks with the sugar in a large bowl until they begin to look pale and thick. Sieve in the cocoa powder and a pinch of salt and fold in.
Whisk the whites in a separate clean bowl, until stiff enough to form soft peaks. Fold the whites into the yolk mixture a little at a time and very gently.
Transfer the mixture into the cake tin, smooth the top and bake for 35-40 minutes, until puffed up and set on top. Leave to cool in the tin.
Drain the cherries, retaining the syrup. Mix 100ml of the syrup with the kirsch Cut the cooled cake into three horizontal slices and put on separate plates. Spoon half of the syrup over the slices and allow to sink in.
Whip the cream until thick, then sift in the icing sugar and add the vanilla extract. Whisk until thick and airy, but not too stiff to spread.
To assemble the cake, put a sponge layer on a cake stand or board. Spread with half of the jam, a third of the cream and a third of the cherries.
Carefully place another chocolate sponge on top and press down gently, then repeat the layers.
Place the last sponge on top and press down gently. Use a palette knife to spread the remaining cream on top.
Arrange the remaining cherries on the top and grate chocolate curls all over. Chill the cake for an hour before serving.