Dice your pumpkin to medium sized pieces. Put into a large soup pot along with the Thai curry paste and the diced chilli and fry for approximately 5 minutes, or until the pumpkin begins to soften.
Add the water or chicken stock until the pumpkin is covered, depending on the size of your pumpkin you may need more or less stock. Bring to the boil and and continue to cook for approximately 30 minutes or until the pumpkin has softened.
Process the mixture with either a food processor or a hand mixer (either works fine) until the mixture is smooth. Return the mixture to the heat and pour in the coconut milk. Depending on the level of heat you want, you can increase or decrease the amount heat in the dish.
Serve with fresh basil leaves.
Try and pick a good quality authentic Thai curry paste, rather than a generic brand.