Easy Chicken Shawarma Salad

Name: Easy Chicken Shawarma Salad
Ingredients: 1 Persian cucumber or 1/2 English cucumber; 1/2 cup cherry or grape tomatoes; 1 small red onion; 1 medium romaine lettuce heart; 1 clove garlic; 1/2 cup plain Greek yogurt; 2 tablespoons brine from pickled banana peppers or pepperoncini; 4 tablespoons water, divided; 1 tablespoon tahini; Kosher salt; Freshly ground black pepper; 6 sprigs parsley; 4 tablespoons olive oil, divided; 2 cups shredded, cooked chicken, preferably rotisserie (about 12 ounces); 2 tablespoons shawarma spice blend (see Recipe Note), such as Sadaf or NY Shuk; 1 pita bread; 1/4 cup sliced pickled banana peppers or pepperoncini; 3 ounces feta cheese