In a mixing bowl, combine the cooked chicken, sliced strawberries, diced celery, and chopped red onion.

In a separate bowl, mix together the Greek yogurt, honey, lemon juice, salt, and black pepper.

Pour the yogurt mixture over the chicken and strawberry mixture, and stir until well combined.

Lay a leaf of romaine lettuce on each slice of whole grain bread.

Spoon the strawberry chicken salad onto the lettuce.

Top with another slice of bread, cut in half, and serve.