Dice 1 small onion and 1/2 green bell pepper; sauté in 1 teaspoon hot oil in a Dutch oven over medium-high heat 3 minutes. Whisk in 4 cups chicken broth and 1 (16-ounce) jar spicy black bean dip until smooth. Bring to a boil, and stir in 2 (16-ounce) cans black beans, rinsed and drained, and 2 cups chopped cooked chicken. Cook 5 minutes or until thoroughly heated. Top individual bowls of soup with low-fat sour cream, shredded Cheddar cheese, baked tortilla strips, diced tomatoes, and avocado slices.