Peel, seed and cube pumpkin. Place on a baking tray and roast for 40 minutes.
While the pumpkin cooks, chop onion, ginger, lemongrass and coriander stalks.
Heat coconut oil in a pot at low temperature. Add the onion, ginger, lemongrass and coriander stalks and cook for 10 minutes, stirring often.
When pumpkin is ready, place in a blender or food processor along with the aromatics, broth, fish sauce and lime juice.
Process to desired consistency, adding more broth or water if desired. Adjust seasoning and serve garnished with coriander leaves and sliced chilli. Add a splash of coconut milk if you wish.