Prep: 1. Chop onion, garlic and green pepper. Make: 1. Heat oil in a Dutch oven or large sauce pot over medium heat. Add onion, green pepper and garlic, and cook until softened, about 8 minutes. 2. Add beef and cook until no longer pink, about 5 minutes. Add tomato paste, chili powder and cumin and cook, 1 minute. 3. Add tomatoes, beans and water. Bring to a boil, then reduce to a simmer. Cook until thickened, about 30 minutes. Add vinegar and season with salt and pepper. 4. Just before chili is done dice avocado. 5. Serve with diced avocado on top.