2To make the dressing, put the tahini, lemon juice, garlic, and a pinch of salt into an airtight jar; close the jar and shake vigorously. Add the olive oil and shake again. Thin with water until pourable, if necessary. Set aside.
3Place the salad greens in a wide, shallow salad bowl, drizzle with a little dressing, and toss to coat. Scatter with the cucumber, tomatoes, green onion, and feta. Top with falafel and crumbled pita chips. Serve, passing additional dressing on the side.