Heat the oil in a medium pot, add the shallots, garlic, celery, ground cumin, ground coriander and a little salt, and sauté on low heat for 12 minutes, to soften the vegetables.
Add the pumpkin, bay leaves, lime leaves, chipotle flakes and water. Bring to a boil and simmer for 15 minutes, or until the pumpkin is soft. Add the corn and cook for five minutes.
Use a slotted spoon to lift out about half of the vegetables, and remove and discard the bay and lime leaves. Blitz the remaining soup until smooth, then return the vegetables to the pot and bring to a light simmer. Add a little water if you find it too thick. Stir in half the soured cream and taste for seasoning.
Divide the soup into six bowls, squeeze the juice of half a lime into each portion, drop about a tablespoonful of soured cream in the middle and scatter over the torn coriander leaves.