In a small bowl, whisk together sour cream (or Greek yogurt), lime juice, olive oil, ground cumin, and chili powder until smooth. Season with salt and pepper to taste. Set aside.

In a large mixing bowl, combine cooked chicken, black beans, corn, red bell pepper, red onion, cherry tomatoes, avocado, and cilantro. Gently mix until well-distributed.

Pour the dressing over the salad mixture and gently toss until everything is coated.

Transfer to a serving platter or bowls, sprinkle with shredded cheese and optional tortilla strips. Serve immediately or chill for 30 minutes.