Prep the chicken: If using rotisserie chicken, remove the skin and bones, then chop or shred. Leftover grilled or poached chicken works too.
Mash the avocado: In a large bowl, scoop out the avocado flesh. Add lemon juice, a pinch of salt, and pepper.
Mash with a fork until mostly smooth with some small chunks.
Build the base: Stir in the red onion, celery, and herbs. Add the garlic and cumin if using.
Add chicken: Fold in the chicken until everything is well coated. If it looks dry, mix in a spoonful of Greek yogurt or a drizzle of olive oil.
Taste and adjust: Add more lemon juice, salt, and pepper as needed.
The flavors should be bright and balanced.
Serve your way: Spoon it onto toast, tuck it into a wrap, scoop into lettuce cups, or pile onto a salad bowl. Add any optional toppings you like.