Whisk together broth, soy sauce, sugar and cornstarch. Place chicken in a separate bowl. Pour half of marinade over chicken and add crushed red pepper; stir. Set aside remaining marinade. Cover and chill chicken for 15 minutes.
Warm a large skillet over medium-high heat. Add 1 Tbsp. oil. Remove chicken from marinade (discard marinade), add chicken to skillet and stir-fry until cooked through, 3 to 4 minutes. Add half of ginger, garlic and white parts of scallions and cook 1 minute. Transfer to a plate.
Add remaining oil to skillet. Stir-fry peppers, peas and remaining ginger, garlic and white parts of scallions until cooked through, 2 minutes. Return chicken to skillet; add reserved marinade and salt. Sauté 1 to 2 minutes, until sauce thickens. Top with cashews and scallion greens.