How to Make It
1. To prepare falafel, combine 6 cups water and chickpeas in a large bowl; let stand at room temperature 8 hours or overnight. Drain.
2. Preheat oven to 450°F.
3. Combine chickpeas, onion, and next 9 ingredients (through ground red pepper) in a food processor; pulse until coarsely chopped. Divide and shape mixture into 16 (1/2-inch-thick) patties (about 1/3 cup per patty).
4. Heat a large cast-iron skillet over medium-high. Coat pan with cooking spray. Place 8 patties in pan; coat patties with cooking spray. Cook 2 to 3 minutes on each side or until browned. Place on a wire rack set on a baking sheet. Repeat procedure with cooking spray and remaining patties. Place baking sheet in oven; bake at 450°F for 10 minutes. Reserve 8 falafel patties for Falafel Pizza and Falafel, Feta, and Tomato Salad.
5. To prepare pita sliders, combine yogurt, mayonnaise, dill, and 1/4 teaspoon black pepper in a bowl. Cut off top fourth of each pita (reserve for another use). Spoon about 1 tablespoon yogurt mixture into each pita pocket; top with 1 falafel patty, 1 tomato slice, 1/4 cup arugula leaves, and about 1/4 cup red onion slices.