Make soup:

Set aside ¼ cup of the coconut milk for the soup topping.

Heat the butter and olive oil in a large sauté pan over medium heat. Add the onion and the celery and cook, stirring occasionally, until they are limp. When onions and celery are limp add the garlic, lemon grass and ginger and curry paste. Cook an additional minute or two or until ginger, lemongrass, etc. are aromatic. Do not let garlic brown. Put the onion mixture into the pitcher of a blender and add approximately one cup of the chicken broth. Process the onion mixture until it is completely pureed, then pour it into a large soup pot. Add remaining broth and stir to blend. Bring the soup to a boil, then reduce to a simmer. Simmer 20 minutes.

Make topping: Place all ingredients into a blender or the bowl of a mini food processor. Process until pureed. Set aside in a small bowl or wrap and refrigerate for a day or two. Makes about 2/3 cup.

Finish Soup: Add the nam pla, cayenne, pumpkin OR butternut squash puree, and remaining coconut milk; stir to blend. Allow the soup to heat but not boil; add the lime juice, the chicken if using, and salt and pepper to taste. Pour servings of fully heated soup into soup bowls, garnish with a large spoonful of Lime-Cilantro Topping. Serve immediately.* Makes 6 to 8 servings.