Stuffed Cabbage

INGREDIENTS

• 2 quarts water
• 1 large green cabbage (about 2 1/2 pounds)
• 2 tablespoons unsalted butter
• 1 large onion, chopped
• 1 garlic clove, finely chopped
• 2 cups cooked rice
• 8 ounces ground beef
• 8 ounces ground pork
• Coarse salt and freshly ground pepper
• 1 tablespoon dried parsley flakes
• 1 medium green pepper, grated
• 2 celery stalks with leaves, finely chopped
• 4 cups tomato puree
• 1 Granny Smith apple, peeled, cored, and chopped
• 1/2 cup sour cream, plus more for garnish