In a large mixing bowl, start by combining the shredded chicken breast, plain Greek yogurt, and the optional mayonnaise. Mix thoroughly until all components are well blended and creamy.
Next, add the diced celery for crunch, the sweet diced red grapes, and the chopped walnuts for a delightful texture. Also, incorporate the Dijon mustard, fresh lemon juice, and garlic powder. Stir well to ensure all ingredients are evenly distributed.
Taste the mixture and season with salt and pepper according to your preference, making adjustments as needed to achieve your desired flavor.
For assembly, take two slices of whole-grain bread and layer each with a crisp lettuce leaf to create a barrier that keeps the bread from getting soggy. Spoon a generous amount of the chicken salad mixture atop each lettuce leaf.
Carefully place another slice of bread over the chicken salad and press down gently. Cut each sandwich in half diagonally for a more appealing presentation. If you are using wraps, place the mixture in the center of the wrap, fold both sides inward, and then roll tightly from the bottom to the top.
Repeat the process with the remaining ingredients to create additional sandwiches as needed.
Notes
Serve on a decorative platter with fresh herbs for garnish.