Heat olive oil in large dutch oven or pot over medium heat.Add onion, celery and carrots, stirring and cooking for about 15 minutes, until softened.Stir in garlic and cook for 1 minute. Add chicken, chicken broth, pumpkin, yogurt, cumin (or other preferred seasoning), chili powder, salt, pepper and garlic salt. Stir to combine. Bring to boil, lower heat and simmer about 10 minutes. Taste and season accordingly with additional seasonings as needed.Garnish with fresh cilantro, avocado, cheese and tortilla chips, if desired.