1 ½ pounds boneless, skinless chicken thighs, trimmed and cut into ½-inch cubes
¼ cup soy sauce, divided
1 tablespoon cornstarch
1 tablespoon Chinese rice wine or dry sherry
1 tablespoon Chinese black vinegar or sherry vinegar if you can't find Chinese vinegar
½ teaspoon white pepper
1 tablespoon packed dark brown sugar
2 teaspoons toasted sesame oil
1 tablespoon minced garlic
2 teaspoons grated fresh ginger
2 tablespoons plus 1 teaspoon vegetable oil, divided
½ cup dry-roasted peanuts
10 dried arbol chiles, halved lengthwise and seeded (I used 10. 10 was too hot maybe try 7 or 6)
1 teaspoon Sichuan peppercorns, ground coarse
2 celery ribs, cut into ½-inch pieces
5 scallions, white and light green parts only, cut into ½-inch pieces
BEFORE YOU BEGIN
Kung pao chicken should be quite spicy. To adjust the heat level, use more or fewer chiles, depending on the size (we used 2-inch-long chiles) and your taste. Have your ingredients prepared and your equipment in place before you begin to cook. Use a spice grinder or mortar and pestle to coarsely grind the Sichuan peppercorns. If Chinese black vinegar is unavailable, substitute sherry vinegar. Serve with white rice and a simple vegetable such as broccoli or bok choy. Do not eat the chiles.
1 For the Chicken and Sauce: Combine chicken, 2 tablespoons soy sauce, cornstarch, rice wine, and white pepper in medium bowl and set aside. Stir vinegar, sugar, oil, and remaining 2 tablespoons soy sauce together in small bowl and set aside.
2 For the Stir-Fry: Stir garlic, ginger, and 1 tablespoon oil together in second small bowl. Combine peanuts and 1 teaspoon oil in 12-inch nonstick skillet over medium-low heat. Cook, stirring constantly, until peanuts just begin to darken, 3 to 5 minutes. Transfer peanuts to plate and spread into even layer to cool. Return now-empty skillet to medium-low heat. Add remaining 1 tablespoon oil, arbols (careful! I used 10 and it was way too hot), and peppercorns and cook, stirring constantly, until arbols begin to darken, 1 to 2 minutes. Add garlic mixture and cook, stirring constantly, until all clumps are broken up and mixture is fragrant, about 30 seconds.
3 Add chicken and spread into even layer. Cover skillet, increase heat to medium-high, and cook, without stirring, for 1 minute. Stir chicken and spread into even layer. Cover and cook, without stirring, for 1 minute. Add celery and cook uncovered, stirring frequently, until chicken is cooked through, 2 to 3 minutes. Add soy sauce mixture and cook, stirring constantly, until sauce is thickened and shiny and coats chicken, 3 to 5 minutes. Stir in scallions and peanuts. Transfer to platter and serve.