Ukrainian Chicken Soup

Name: Ukrainian Chicken Soup
Ingredients: One 3-pound chicken, neck reserved; 2 medium onions—1 unpeeled and quartered, 1 chopped into 1-inch pieces; 2 carrots, scrubbed and cut into 2-inch pieces; 2 celery ribs, cut into 2-inch pieces; 1 large unpeeled garlic clove, smashed; 1 teaspoon whole black peppercorns; 3 1/2 quarts water; 1 large fresh bay leaf; 6 parsley sprigs; 2 thyme sprigs; Kosher salt; 2 tablespoons unsalted butter; 8 cups chopped green cabbage (1 pound); 1 cup thinly sliced garlic dill pickles (4 ounces); 1/4 cup tomato paste; 1 tablespoon sweet paprika; Freshly ground pepper; 1/2 cup reserved pickle juice; 1/4 cup chopped fresh dill, plus more for garnish; Sour cream, for garnish