Circassian Chicken Çerkez Tavugu

Name: Circassian Chicken (Çerkez Tavugu)
Ingredients: 2 ½ pounds bone-in chicken breasts; 4 cups low-sodium chicken broth; 2 cups walnuts, plus more for garnish; 2 large cloves garlic; ½ cup chopped fresh cilantro, divided, plus more for garnish; 1 teaspoon salt; ¾ teaspoon ground coriander; ¾ teaspoon paprika; ½ teaspoon Aleppo pepper (see Tips), plus more for garnish; ½ teaspoon dried savory or tarragon; ¼ teaspoon ground cinnamon; ¼ teaspoon ground fenugreek (see Tips); ¼ teaspoon saffron threads (see Tips); 2 tablespoons butter; 1 tablespoon extra-virgin olive oil; 1 small onion, finely chopped; 3 tablespoons red-wine vinegar, divided; Chopped red onion & pomegranate seeds for garnish