Add the chickpeas, parsley, cilantro, onion, 2 minced garlic cloves, cumin, coriander, salt, pepper, baking powder, and flour to a food processor. Pulse until the mixture is finely chopped and holds together when pressed.

Shape the mixture into 12 small patties, each about 2 inches wide. Place them on a plate.

Heat 1/4 inch of vegetable oil in a large skillet over medium heat. Fry the patties in batches for 3 to 4 minutes per side until deep golden and crisp. Drain on paper towels.

Warm the pita breads briefly in a dry skillet or microwave.

Stir together the tahini, lemon juice, remaining minced garlic clove, and water in a small bowl until smooth and pourable.

Fill each pita with 3 falafel patties, lettuce, tomato, and cucumber. Drizzle generously with tahini sauce before serving.