Heat the oil in a large pot over medium heat. Add the onion, green pepper, carrot and parsnip and cook 5 minutes. Add remaining ingredients, except green onions, and bring to a boil. Lower heat, loosely cover and gently simmer for 30-40 minutes, stirring occasionally, until the vegetables are tender and the chili is rich in flavour. Sprinkle bowls of the chili with chopped green onions and serve with taco chips, grated cheese and sour cream, if desired.