Cut the figs in half lengthways, without slicing all the way through. Halve the plums and remove the stones. Put the figs and plums into a shallow, ovenproof dish that will hold the fruit in a single layer.
Mix the wine, vodka, 150g of the sugar and 4 tbsp of the cassis in a pan and heat, stirring to help the sugar dissolve. Simmer until reduced by one-third, then pour it over the fruit. Sprinkle the rest of the sugar on top of the fruit.
Bake in the oven for 25-30 minutes. (If you are using grapes instead of blackberries, add them 15 minutes before the end of the cooking time.) The fruit should be soft, but not collapsing, and slightly caramelised on top.
Let the fruit cool, then add the blackberries, if using. Pour a slug of vodka over the fruit and drizzle with the remaining 2 tbsp of cassis.
Remove the seeds from the cardamom pods and grind them in a mortar, or in a heavy bowl using the end of a rolling pin.
Put the cream in a bowl, add the crushed cardamom and whip the cream, adding icing sugar to taste. Serve with the fruit.