• Pat the chicken dry with a paper towel; season generously with salt and pepper.

In a large frying pan over medium-high heat, warm 1 tablespoon [2 TBL] oil until hot but not smoking. Add the chicken and cook, turning occasionally, until lightly browned and cooked through, 3 to 4 minutes per side for thighs, 4 to 6 minutes per side for breasts. Transfer to a plate to cool slightly. Using a fork, shred the chicken into bite-size pieces and sprinkle with the sumac. 

While the chicken cooks and cools, start preparing the pita chips.

• Cut each pita bread into 8 wedges.

In another large frying pan over medium heat, working in batches if needed, spread the pita wedges in an even layer, drizzle or brush with 1 to 2 teaspoons oil, and season with salt and pepper. Toast, turning occasionally, until lightly browned and crisp, 6 to 8 minutes. Transfer to a plate, season lightly with salt, and let cool slightly.
While the pita toasts, prepare the remaining ingredients.

• Trim the root end from the romaine heart; coarsely chop the leaves.
• Peel the cucumber, if desired; cut the cucumber in half lengthwise, then on the diagonal into ¼-inch-thick slices.
• Cut away the core from the tomato; coarsely chop the tomato.

In a large bowl, stir together the lemon-tahini dressing base and 2 tablespoons [¼ cup] oil; season to taste with salt and pepper. Add the romaine, cucumber, tomato, chicken, and feta. Break up the pita chips, add as many as you like, and toss to combine. Season to taste with salt and pepper.

Transfer the chicken shawarma salad to individual bowls and serve any remaining pita chips on the side.