Chicken Caesar Lettuce Cups

Preheat oven to 400 degrees F. Toss together bread and oil in a large bowl; spread in a single layer on a rimmed baking sheet. Bake in preheated oven until golden brown and toasted, about 10 minutes, stirring once halfway through cooking. Set aside to cool.

While bread toasts, whisk together yogurt, water, mayonnaise, Parmesan, mustard, salt, and pepper in a large bowl. Cut 5 inches from the top of each romaine lettuce heart; set aside 8 of the largest leaf tops for lettuce cups. (Save remaining leaves for another use or discard.) Chop bottom section of each romaine lettuce heart into bite-size pieces. Add chopped lettuce, chicken, and cooled bread to bowl with dressing; toss to coat. Divide evenly among 8 reserved lettuce cups.