1. If needed, poach or roast 2-3 boneless, skinless chicken breasts; shred or dice after cooling.
2. Mash the avocados until mostly smooth with a few small chunks for texture.
3. In a large bowl, combine yogurt (if using), lime juice, Dijon mustard, olive oil (if using), ground cumin, salt, and pepper with the mashed avocado.
4. Add chopped red onion, celery, cucumber, jalapeño, and herbs to the avocado dressing; mix well.
5. Add shredded chicken and gently fold to coat all the pieces.
6. For best flavor, refrigerate for 15-30 minutes before serving. Serve on lettuce cups, in a sandwich, or over mixed greens.
7. Garnish with toppings like toasted almonds, cherry tomatoes, or a drizzle of olive oil.