Heat the olive oil in a large saucepan, then add the parsnips, onion, carrots, celery, sweet potato and potatoes. Cook for 5 minutes, stirring frequently. Add the caraway seeds, stock powder and water. Simmer for 15 to 20 minutes, or until vegetables are cooked through. When the vegetables are cooked, turn off the heat, add the parsley and stir through. Serve and top with salt and pepper if desired.