Gather all salad ingredients. Dice or shred about 2 cups of cooked chicken breast and place it into a large mixing bowl. Dice 1 ripe avocado, 1 cup of celery, and ¼ cup of red onion. Finely chop ¼ cup of fresh parsley and 2 tablespoons of fresh dill. Combine these ingredients and set aside.

In a separate medium bowl, whisk together ¾ cup of Greek yogurt, juice of 1 lemon, 1 tablespoon of Dijon mustard, ¼ teaspoon of garlic powder, and a pinch of salt and black pepper. Whisk until smooth and creamy.

Pour the dressing over the chicken and vegetable mixture. Gently toss until everything is evenly coated without mashing the avocado.

Taste the salad and adjust seasoning if necessary by adding more salt, pepper, or lemon juice.

Spoon the salad mixture into large butter lettuce leaves. Aim for about ½ cup of salad per leaf and garnish if desired. Serve immediately.