Heat butter in a large pot (8-quart) on medium high heat. Add the onions and cook for 3-4 minutes, until softened. Add the garlic, cumin, oregano, cinnamon and chipotle, cook for 1 minute more.
Add the pumpkin, chicken stock and salt. Bring to a simmer, reduce the heat and simmer for 20 minutes, partially covered. Add cream, simmer 10 min more.
Remove the soup from heat. Working in batches of 2 cups each, purée the soup in batches, holding down the lid to the blender tightly while puréeing, and starting on a slow speed. Return the puréed soup to the pot.
Hold warm till ready to serve, garnish top of soup with toasted pecans, cilantro and avocado.