⅓ cup soy sauce
⅓ cup Shaoxing wine or dry sherry
1 tablespoon packed brown sugar
1½ pounds boneless, skinless chicken thighs, trimmed and cut into 2-inch pieces
3 tablespoons vegetable oil
1 (2-inch) piece ginger, peeled, halved lengthwise, and sliced into thin half-rounds
12 garlic cloves peeled and halved lengthwise
½ - ¾ teaspoon red pepper flakes
6 scallion, white and green parts separated and sliced thin on bias
1 tablespoon water
1 teaspoon cornstarch
1 cup Thai basil leaves, large leaves sliced in half lengthwise
1 tablespoon toasted sesame oil
Whisk soy sauce, wine, and sugar together in a medium bowl. Add chicken and toss to coat; set aside.
Heat vegetable oil, ginger, garlic, and pepper flakes in a 12-inch nonstick skillet over medium-low heat. Cook, stirring frequently until garlic is golden brown and beginning to soften 8 to 10 minutes.
Add chicken and marinade to skillet, increase heat to medium-high, and bring to simmer. Reduce heat to medium-low and simmer for 10 minutes, stirring occasionally. Stir in scallion whites and continue to cook until chicken registers about 200 degrees, 8 to 10 minutes longer.
Whisk water and cornstarch together in a small bowl, then stir into sauce; simmer until sauce is slightly thickened, about 1 minute. Remove skillet from heat. Stir in basil, sesame oil, and scallion greens.