In a large saucepan, sauté onions & garlic in butter until translucent and slightly caramelized. Add curry powder & coriander and sauté 2 minutes longer. Remove from heat and stir in the pumpkin and salt. In batches, spoon mixture into a food processor or blender and process until smooth adding broth as necessary for blending. Return mixture to a large soup pot. Stir in the remaining broth, cream & half & half. Heat but do not boil. Serves about 8.