First we need to make a paste, so put the lemon grass, garlic, chillies, ginger, lime leaves and juice into a blender and blend until smooth (the smoother the paste the nicer the soup, so take your time).
Put the chopped pumpkin into an ovenproof dish, sprinkle with sea salt and oil then roast for about 35 mins at 200c/ 400f/ gas mark 6 until soft. Gently fry the shallots and cumin seeds, then add half the paste and cook for 5 mins to release the fragrance.
Add pumpkin and cook for a couple of mins, then add the stock and boil it all up. When it’s got to the boil simmer for about 7-8 mins. Put the soup and coconut milk in a blender and blend until smooth.
For the rice balls
Pulse half the rice then combine with the rest of the rice, paste, coriander and nuts, season, mould into 25mm balls and deep fry until golden.
To serve, spoon a big load of soup into the bowl, top with coriander, cucumber and mint and a few balls around the bowl.