Place olive oil in a large heavy-based saucepan over medium heat.
Add shallots,ginger,lemongrass and chilli powder and cook for 3-5 minutes or until soft and translucent.
Add pumpkin and stock,bring to the boil and simmer gently until pumpkin is very tender.
In a blender,puree soup in small batches until very smooth.
Rinse saucepan and place puree in it. Add coconut cream,season with salt,pepper and fish sauce,and heat through without allowing soup to boil.
Taste and adjust seasoning,then add lime juice and finely shredded lime leaves (keep some aside for garnish).
Ladle soup into bowls and garnish with lime leaves,coriander (if using) and macadamias.