Add water, onion, bay leaf, parsley, thyme, salt & pepper, bring to a boil. Lower heat and simmer 1 hour covered. Combine garlic, coriander, chili powder & soy sauce, slowly stir into broth, bring to boil. Add chicken, shrimp, and mushrooms. Cook until chicken is tender and shrimp turns pink. Before serving stir in sprigs and scallions.