Seed and finely chop chile.  Melt sugar over low heat in skillet until it is a light brown caramel color.  Add chile and pistachios and stir to coat.  Turn mixture out of pan onto foil or wax paper and let cool.  Pare pumpkin or squash and cut into cubes.  Peel and chop shallots.  Cut lemon grass into 4-inch lengths.  Melt butter in large saucepan, add shallots and lemon grass, cover and cook 1 minute.  Add cubed pumpkin or squash, stock, pepper and cloves.  Cover and simmer over low heat for 15 to 20 minutes or until tender.  Discard lemon grass.  Puree pumpkin mixture in food processor or electric blender.  Return to saucepan.  Whisk in sour cream, heat gently then pour into wide soup bowls.  Top with cilantro and caramelized pistachios.