Preheat the oven to 180 °C/gas 4.

Prepare the shortcake. Cream butter and vanilla sugar in a bowl until light and fluffy. Mix together flour and semolina. Gradually add to butter until a crumbly dough is formed. Carefully and gently knead the dough until it binds together and surface is smooth. Roll out thinly to line 6 loose bottomed 4 inch tart tins. Prick bases. Chill well for an hour. Line with foil and baking beans.

Bake pastry cases blind for 20 minutes or so in preheated oven until cooked through. Remove beans and foil and continue drying out in oven if necessary. Prepare chocolate filling. Break chocolate into squares. Place in a bowl over a pan of water or a double boiler. Add cognac to chocolate. Heat gently until chocolate is melted. Beat eggs in a bowl. Blend in cornflour and sugar and add a little cream, if necessary.

Heat remaining cream in a saucepan with vanilla pod until almost boiling. Stir hot cream into blended egg mixture.

Rinse cream pan in cold water. Return mixture to pay and add melted chocolate. Cook gently, stirring constantly, until mixture thickens and cornflour is cooked. Taste mixture to check it is not floury. This will take between 6-8 minutes. Remove vanilla pod.

Cool filling slightly. Soften butter and allow to cool. Beat softened butter into chocolate filling. Pour into chilled tarts and leave to set. When cold make chocolate leaves with some melted chocolate and use to decorate the tarts.