Marinate chicken in yogurt, ginger-garlic paste, and biryani spices for 30 minutes. In a pot, sauté onions, add marinated chicken, and cook partially. Layer partially cooked basmati rice over the chicken, sprinkle with saffron milk and fried onions. Cover tightly and cook on low heat for 20–25 minutes (dum method). Gently mix and serve with raita.