3 medium eggplants, cut into ½-inch cubes (8 cups)
¾ teaspoon salt, divided
¾ teaspoon ground black pepper, divided
3 ½ tablespoons olive oil, divided
¼ cup quick-cooking bulgur
⅔ cup quinoa, rinsed and drained
⅔ cup chopped fresh mint, plus sprigs for garnish
⅓ cup chopped parsley
1 cup small mixed bell peppers, diced
2 tablespoons lemon juice
1 cup cooked chickpeas
½ cup finely chopped red onion