Process garbanzo beans, onion, parsley, garlic, cumin and oregano in a food processor until smooth; season to taste with lemon juice, salt, and pepper. Stir in 1/2 cup bread crumbs, raisins and egg yolk.
Form bean mixture into 16 patties, using about 1 1/2 Tbsp for each. Coat patties with remaining 1/2 cup bread crumbs.
Spray large skillet with cooking spray; heat over medium heat until hot. Cook falafel over medium heat until browned on the bottom, 2 to 3 minutes. Spray tops of falafel with cooking spray and turn; cook until browned on the bottom, 2 to 3 minutes. Arrange 4 falafel on each plate; serve with Tomato-Cucumber Relish.
To make Tomato-Cucumber Relish:
Combine tomato, cucumber, yogurt and mint leaves in small bowl. Season to taste with salt and pepper.