1. Heat 2 tablespoons of oil in a large saucepan and gently cook finely chopped onion, grated ginger, chilli (seeds removed and finely chopped) and crushed garlic for 5 minutes. Add the pumpkin and cook for a further minute.
2. Add the chicken stock and bring to the boil, then simmer for 15 minutes until the pumpkin is just tender. Add the coconut cream and fish sauce and simmer for a further 5 minutes. Remove the soup from the heat and purée in batches in a blender until smooth.
3. Cook the prawns in a little oil in a frying pan until they turn pink. Pour the hot soup into bowls and top with crisp fried shallots, prawns and coriander leaves.

Tip: Crisp fried shallots are available in Asian food stores or you can make your own by cooking very finely sliced shallots or onion in hot oil until crisp.