Chicken and Cashew Stir Fry

Name: Chicken and Cashew Stir-Fry
Ingredients: 1 bunch scallions; 1 pound skinless boneless chicken thighs; 1/2 teaspoon salt; 1/4 teaspoon black pepper; 3 tablespoons vegetable oil; 1 red bell pepper, chopped; 4 garlic cloves, finely chopped; 1 1/2 tablespoons finely chopped peeled fresh ginger; 1/4 teaspoon dried hot red-pepper flakes; 3/4 cup reduced-sodium chicken broth; 1 1/2 tablespoons soy sauce; 1 1/2 teaspoons cornstarch; 1 teaspoon sugar; 1/2 cup salted roasted whole cashews