1. Preheat the oven to 180°C/fan 160°C/350°F/gas mark 4. Butter a 25cm round, deep cake tin and line the base and sides with baking parchment.
2. To de-seed the cardamom pods, split the husks with the point of a knife, empty all the little seeds into a mortar and grind them to a powder with the pestle. Sift to remove any pieces of husk.
3. Put the rice into a large saucepan of cold unsalted water, bring to a boil, then boil for three minutes. Drain.
4. Return the rice to the rinsed-out pan with the milk, lemon grass, cardamom powder and bay leaves. Add all but 1 tbsp of the sugar. Bring to a boil, then reduce the heat and simmer gently for 20 minutes, stirring occasionally. Allow to cool, still stirring occasionally, then remove the lemon grass and bay leaves.
5. Mix the whipping cream and coconut cream together and stir into the rice with the egg yolks. Whisk the egg whites until firm, then whisk in the remaining 1 tbsp of sugar until softly stiff. Fold into the rice mixture, and pour into the prepared tin.
6. Bake in the preheated oven for 35–45 minutes. The top should still wobble very slightly when shaken. Cool completely in the tin, then turn out on to a serving plate and remove the papers.
7. Loosen up the quark (or mascarpone) with a whisk, and lightly whip the double cream until just firm. Mix the two together with the vanilla, adding the lemon zest and sugar to taste. Spread over the top and sides of the cake, swirling with a palette knife.
8. Decorate with a few physalis (I twisted the leaves back up). This cake can be made a day ahead and stored in the fridge