Place the chicken in a bowl with 1/4 cup cornstarch and salt and pepper. Toss to coat chicken evenly.
Heat the vegetable oil in a large pan over medium high heat. Add half of the chicken in a single layer. Cook for 3-4 minutes per side or until browned.
Transfer the cooked chicken to a plate and repeat the process with the remaining raw chicken pieces.
Remove all the chicken from the pan. Drain any excess oil, leaving 1 teaspoon of oil in the pan. Add the garlic and ginger and cook for 30 seconds.
In a bowl, whisk together the chicken broth, soy sauce, rice vinegar, ketchup, sweet chili sauce and brown sugar. Pour the sauce mixture into the pan.
Bring the sauce to a simmer. Place the cornstarch in a bowl with 2 tablespoons cold water and whisk to combine.
Pour the cornstarch into the pan and bring to a boil. Cook for 1 minute or until sauce has just thickened.
Place the chicken and cashews in the pan and toss to coat with the sauce. Sprinkle with green onions and serve.