Collard Green and White Bean Gratin

Name: Collard Green and White Bean Gratin
Ingredients: 1 pound collard greens, stems and tough ribs removed; 5 garlic cloves, divided, 1 crushed and 4 chopped; 1/4 cup extra-virgin olive oil, divided; 1 medium onion, chopped; 1 small red bell pepper, cut into 1/2-inch pieces; 3 cups cooked white beans, 1/2 cup cooking liquid reserved; 1/2 cup diced or chopped cooked ham-hock meat, sausage, chorizo, or bacon; 1/4 cup freshly grated Parmigiano-Reggiano, divided; 1 tablespoon finely chopped fresh rosemary leaves; Kosher salt and ground black pepper; 1/4 cup medium-coarse fresh bread crumbs