Combine first 5 ingredients in a large bowl. Gently stir avocado into chicken mixture until combined.
Place 1 lettuce leaf onto each of 4 bread slices. Spoon chicken mixture evenly onto each lettuce leaf. Top with remaining bread slices.
Serve with: Herbed Tomato-Cucumber Salad
Shortcut Kitchen Tip
To peel, seed, and dice an avocado, cut into the avocado vertically using a sharp knife; you'll hit the large seed in the center, so don't expect to be able to cut all the way through the fruit.
Cut around the seed; twist both sides. Pull the halves apart. Whack the seed with the knife blade; then gently twist the knife, and pull to remove the seed, which will be stuck on the blade. Gently slice several horizontal and vertical lines through the flesh, but not through the skin. Use a spoon to gently scoop the diced flesh from the shell.
