For the cake

Preheat oven to 170C. Gently melt the chocolate in a microwave or over a double boiler. In a bowl, combine the melted chocolate with the soft butter and beat until creamy. Slowly and gradually beat in the sugar and egg yolks (adding one at a time). Fold in the sifted flour. Beat the whites until stiff with a pinch of salt and very gently fold through the mixture. Pour into a lined and greased 26cm spring-form tin. Bake for 40-50 minutes or until a skewer comes out clean. Remove from the oven and allow to cool.

For the cherries

Mix the cornflour with enough cherry juice to make a paste. Combine the rest of the juice with the cornflour paste and put into a saucepan with the desired amount of sugar. Cook, stirring, until it boils and thickens. Add the cherries and liqueur, remove from heat and allow to cool.

For the ganache

Gently heat the chocolate and cream in a saucepan, stirring constantly until the chocolate has melted and the mixture is smooth. Do not let it boil. Pour into a bowl and allow the ganache to cool until you have the right consistency, i.e. thin enough to pour but thick enough so it stays on the cake. It's about right at room temperature. Pour over the top of the cake and wait until it is set.  

To assemble

Whip the 250ml cream with the 1 tablespoon extra castor sugar until thick. Cut the cake in half horizontally. Sprinkle the bottom layer with a little extra liqueur and spread over the cherry mixture. Top with the cream then place the other half of the cake on the top. Pour over the ganache and allow to set before cutting.

To serve 

Although this cake is best eaten on the day, it is still great the next day.