Put the butter and sugar into a bowl and beat well until light and creamy. Beat in the eggs one at a time. Add the chocolate and vanilla extract. Mix well. Gradually add the sifted flour and baking powder, until well mixed.

In a separate bowl, whisk the egg whites to soft peaks. Fold a third of the egg whites into the chocolate mixture to loosen it. Then gently fold in the remain egg whites.

Spoon the mixture into the prepared 2 (22cm) cake pans. Bake in the oven to 170ºC for 35 minutes, or until set. Leave to cool in the pan before putting into a serving plate.

Lightly spread the jam between cake layers and then place the other cake on top. Brush the top and sides of the cake with remaining jam.

Melt the chocolate and heavy cream over low heat, stirring continously. When melted remove from the heat and stir in the icing sugar. Stir for 2-3 minutes until it begins to thicken.

Spread the icing over the top and sides of the cake and leave to set. Chill for 3 hour or until ready to serve.