Step 1

If using tuna or chickpeas, drain them, then in a small bowl mash them with a fork (if using chicken, chop and add to a small bowl). Stir in the celery, scallion, mayonnaise, mustard, Parmesan, if using, salt, pepper and seasoning, if using. Taste, and adjust seasoning as desired. Split the salad between two pieces of the bread, top with the remaining bread and serve.

Step 2

NOTE: If desired, spread the bread with mayonnaise or hummus before building the sandwich, and add lettuce or other greens for crunch.