1 pound ground dark-meat turkey (93 percent lean)
2 garlic cloves, minced
1 large egg, lightly beaten
1/2 cup plain dried breadcrumbs
1/4 cup grated Parmesan, plus more for serving
Coarse salt and ground pepper
1 tablespoon olive oil
1 medium onion, halved and thinly sliced
2 cans (14 1/2 ounces each) reduced-sodium chicken broth
2 cans (14 1/2 ounces each) diced tomatoes in juice
2 heads escarole (2 pounds total), cored, trimmed, and coarsely chopped
1. In a bowl, combine turkey, garlic, egg, breadcrumbs, Parmesan, 1 teaspoon salt, and 1/4 teaspoon pepper. Using 1 tablespoon for each, roll mixture into balls.
2. In a large pot, heat oil over medium. Cook onion, stirring occasionally, until softened, 3 to 4 minutes. Add broth and tomatoes (with juice); bring to a simmer. Add meatballs; cook, without stirring, until meatballs float to surface, about 5 minutes.
3. Add as much escarole to pot as will fit. Cook, gradually adding remaining escarole, until wilted and meatballs are cooked through, about 5 minutes more. Thin soup with water if desired; season with salt and pepper. Serve soup sprinkled with more Parmesan.