Trim thighs and cut into 1-inch cubes. In a medium bowl mix soy sauce, rice wine vinegar, cornstarch, the chopped green onion, and the ginger slices. Add chicken, toss to coat, cover and marinate for 10–15 minutes.

Line a plate with paper towels and set aside. Remove the ginger slices before frying.

Pour oil into a medium saucepan (about 2 inches deep). Heat over medium-high until it reaches 350°F (177°C).

Using tongs, add chicken pieces to the hot oil. Fry in batches for 3–5 minutes until golden and crispy. Don't overcrowd the pot; crowding lowers oil temperature.

Transfer chicken with a slotted spoon to the paper-towel plate.

Wipe out a wok or use a clean pan and add 1 tablespoon vegetable oil. Heat over medium. Add the Szechuan peppercorns and dried red chilies; fry briefly until fragrant, about 1 minute.

Stir in the minced garlic and minced ginger, frying for 20–30 seconds until fragrant.

Add the crispy fried chicken back to the wok. Sprinkle in salt, sugar, and chopped green onion. Toss quickly until everything is evenly coated and heated through. Remove from heat immediately.

Serve immediately with steamed rice or noodles so the chicken keeps its crispness.