Place the chicken in the slow cooker with the rest of the ingredients and stir. Set to low and cook for 6-8 hours. Please note you can use fresh veggies as well. Just before serving, remove one cup of soup mixture and puree with 2 tablespoons of sour cream. Return to slow cooker and stir. Serve soup with a scoop of sour cream and slice of avocado, if desired. Makes approximately four servings.