Parmesan Cheese Broth Pasta Fagioli

Name: Parmesan Cheese Broth Pasta Fagioli
Prep time: 1 h
Cook time: 5 h
Total time: 6 h
Cuisine: Italian
Ingredients: 1 pound Parmesan cheese rinds; 5 leek leaves (from the leeks in the soup base); 5 sprigs fresh parsley; 5 sprigs fresh thyme; 2 teaspoons whole black peppercorns; 12 cups (3 quarts) water; 8 ounces dried chickpeas (about 1 1/4 cups); 8 ounces dried cannellini beans (about 1 1/4 cups); 6 cloves garlic, divided; 4 sprigs fresh oregano, divided; 4 sprigs fresh thyme, divided; 2 sprigs fresh rosemary, divided; 2 bay leaves, divided; 2 teaspoons kosher salt, divided; Freshly ground black pepper; 1 medium white onion; 2 tablespoons unsalted butter; 1 teaspoon kosher salt, plus more as needed; 3 medium carrots (about 8 ounces total); 3 stalks celery (about 6 ounces total), plus the leaves for garnish; 2 medium leeks (about 1 1/2 pounds total); 1 tablespoon olive oil; 12 ounces dried ditalini pasta (scant 2 1/2 cups, or other small soup pasta); Crusty bread or garlic bread, for serving