Preheat the oven to 175°C (340°F/Gas 4). Grease a springform tin approx. 24 cm (9 inch) in diameter. Cut a sheet of baking paper to size and place on the bottom. Grease. Combine the sugar, ricotta, lemon jam, vanilla sugar, lemon zest, cornflour and eggs into a smooth batter. Pour into the tin. Bake the cake until done for approx. 1 hour. Leave to stand in the tin for 15 minutes and carefully transfer the cake to a plate to cool.
Halve the dates and remove the pit. Leave to steep in the Marsala.
In a saucepan bring the jelling sugar, 200 ml (6 fl oz/¾ cup) water, the cinnamon sticks and cardamom pods to a boil. Reduce. Add the dates and the Marsala and allow to slightly thicken. In the meantime soak the gelatine sheets in cold water, squeeze and stir into the warm jelly until dissolved. Or dissolve the powdered gelatine in a tiny amount of warm water and then add to the jelly. Briefly leave the jelly to cool. Using a spoon first remove the spices and then the date halves. Arrange the dates neatly next to each other on the cake. Cover with the rest of the jelly and allow to set before slicing the cake.