FOR SAUCE:
• ¼ cup olive oil
• 1 onion, chopped
• Kosher salt, freshly ground pepper
• 2 garlic cloves, finely chopped
• 2 28-oz. cans crushed tomatoes
• 1 tablespoon light brown sugar
• 1 tablespoon red wine vinegar
• 1 bay leaf
FOR MEATBALLS & SANDWICH:
• Vegetable oil spray
• Turano Bambino Rolls
• ½ cup milk
• 1 pound ground chicken
• 2 ounces finely grated Parmesan, plus more
• 2 tablespoons finely chopped fresh flat-leaf parsley
• 2 garlic cloves, finely chopped
• 2 eggs, beaten
• 1½ teaspoons kosher salt
• ½ teaspoon freshly ground black pepper

SAUCE:
① Heat oil in a large saucepan over medium-high heat. Add onion and season with salt and pepper. Cook, stirring often, until onion is softened and translucent, 8–10 minutes.
② Add garlic and cook, stirring, until fragrant, about 2 minutes. Add tomatoes, sugar, vinegar, and bay leaf and bring to a low simmer.
③ Season with salt and pepper and simmer, partially covered, while you prepare meatballs.

MEATBALLS AND ASSEMBLY:
④ Preheat broiler. Lightly coat a rimmed baking sheet with vegetable oil spray and set aside.
⑤ Combine bread and milk in a small bowl and set aside, tossing occasionally, until milk is completely absorbed, 8–10 minutes.
⑥ Combine chicken, 2 oz. Parmesan, parsley, garlic, eggs, salt, pepper, and soaked bread in a large bowl; gently mix with your hands until ingredients are fully incorporated. Dampen your hands, then form mixture into 12 balls; place 2 inches apart on a prepared baking sheet.
⑦ Broil, rotating pan once, until meatballs are browned, 8–10 minutes. Add meatballs and any juices to the sauce and continue to simmer uncovered, stirring occasionally, until meatballs are cooked through, the sauce is thick and chunky, and flavors have melded, 20–25 minutes.
⑧ Remove from heat and let cool slightly. Top each split roll with a meatball or two, a dab of sauce, and more Parmesan.