Invented in 1950s Taiwan by chef Peng Chang-Kuei, this crowd-pleasing fried chicken dish was adapted for American palates with a chile-spiked sweet-and-sour sauce and has since become a Chinese takeout classic.
Combine chicken, egg white, soy sauce, wine, and 1/2 teaspoon salt in a bowl. Whisk together cornstarch, flour, baking powder, and 1/4 teaspoon salt in another bowl. Let stand while making sauce.
Make the sauce: Whisk soy sauce into cornstarch. Then whisk in wine, sugar, vinegar, and broth.
Heat 1 1/2 inches oil in a deep pot (preferably cast-iron) to 350 degrees. Working in batches, remove chicken from marinade (do not worry about removing excess liquid) and toss in cornstarch mixture. Carefully add to oil and cook until crisp and light golden brown, 2 to 2 1/2 minutes. Transfer to paper towels to drain.
Heat 2 tablespoons oil in a wok over medium. Add chiles, garlic, ginger, and scallion whites. Cook until fragrant, about 1 minute. Stir in sauce mixture and bring to a boil. Add chicken and toss to coat in sauce. Remove from heat. Stir in sesame oil. Garnish with scallion greens and serve immediately with broccoli and rice.