Stovetop Instructions: Heat the oil in a large saucepan with a tight-fitting lid over medium heat; sauté onion, carrots, celery and cabbage for about 5 minutes, stirring well. Raise heat to high and add broth, tomatoes and water. Bring to a boil, reduce heat to low, cover and simmer gently for 1 hour. Remove from heat and add garlic and freshly ground black pepper.
Slow Cooker Instructions: Combine all ingredients in a slow cooker. Cover and cook on low heat setting for 7 to 9 hours (depending on the manufacturer, model and age of your slow cooker), or on high setting for 4 to 6 hours.