Place chicken in a stockpot with water to cover; bring to a boil and cook until juices run clear, at least 20 minutes. An instant-read thermometer inserted into the thickest part of the thigh near the bone should read 165 degrees F (74 degrees C). Remove chicken; set aside to cool. Reserve 1/2 cup of the cooking liquid.

Remove chicken meat from bone; cut meat into 1/2-inch by 2-inch strips. Mix cornstarch and cold water together in a small bowl. Toss meat in 1/2 of the cornstarch mixture.

Heat peanut oil in a wok or large skillet over high heat. Add chicken mixture, ginger, and chiles; cook and stir until fragrant, 2 to 3 minutes. Add reserved cooking liquid, vinegar, rice wine, peppercorns, and salt. Return to boil; cook and stir until mixture is almost dry, about 3 minutes. Stir in spring onions, monosodium glutamate, and remaining cornstarch mixture; cook until sauce is thickened, 2 to 3 minutes more. Drizzle with sesame oil.