Heat the oil in a soup pot over medium heat. Add the onion and leek and cook for a few minutes until soft. Stir in the pumpkin, sweet potato and vegetable stock. Bring to a boil then cover and reduce heat to low.
Simmer for about 15 minutes, or until vegetables are tender. Mash vegetables coarsely using a potato masher. Stir in the coconut milk, season with salt and pepper and serve.