1. Trim any excess fat from lamb and remove silver skin with a small sharp knife; rinse and pat dry. Let lamb stand at room temperature 20 minutes. Season with salt and pepper.
2. Heat 1 tablespoon oil in a large skillet over moderately high heat until hot but not smoking; add lamb and cook, turning, until browned on all sides, about 6 minutes. Transfer lamb to a plate. In same skillet, add onion and 3 tablespoons garlic; cook, stirring, 1 minute. Add wine and simmer 2 minutes, scraping up any brown bits from bottom of skillet. Transfer to slow cooker.
3. Rinse and drain beans in a colander. Pick beans over and add to slow cooker with broth, kale, tomatoes, and herbs. Nestle lamb in center; cook on low heat, covered, until lamb is very tender and begins to fall off bones, about 6 hours.
4. Meanwhile, in clean skillet, heat remaining 2 tablespoons oil over moderate heat. Add remaining 1 tablespoon garlic and cook, stirring, 30 seconds. Add bread crumbs and cook, stirring, until golden brown, about 3 minutes. Transfer bread crumbs to a plate to cool; salt and pepper to taste.
5. Spoon beans onto serving plates and top with lamb. Sprinkle with bread crumbs and garnish with rosemary sprigs. Makes 6 servings.