Martha Stewart's Cashew Chicken

We got this recipe from the Martha Stewart cookbook Lisa got me for Christmas, Food Everyday: Good Food Fast. This is a real go to recipe, and what we usually make when we invite people over for dinner. I'm copying this straight from the Martha Stewart website so there is no way I can mess it (or get in trouble :) ) 
Here's the website: http://www.marthastewart.com/334708/cashew-chicken

• Prep Time30 minutes
• Total Time30 minutes
• YieldServes 

Ingredients

• 1 1/2 pounds boneless, skinless chicken breast, cut into 1-inch cubes
• 1 tablespoon cornstarch
• Coarse salt and ground pepper
• 2 tablespoons vegetable oil, such as safflower
• 6 cloves garlic, minced
• 8 scallions, white and green parts separated, each cut into 1-inch pieces
• 2 tablespoons rice vinegar
• 3 tablespoons hoisin sauce
• 3/4 cup raw cashews (4 ounces), toasted
• White rice, for serving (optional)

Directions

1. In a medium bowl, toss chicken with cornstarch until chicken is coated; season with 3/4 teaspoon salt and 1/4 teaspoon pepper.
2. In a large nonstick skillet, heat 1 tablespoon oil over medium-high heat. Cook half the chicken, tossing often, until browned, about 3 minutes. Transfer to a plate.
3. Add remaining oil and chicken to skillet along with the garlic and white parts of scallions. Cook, tossing often, until chicken is browned, about 3 minutes. Return first batch of chicken to pan. Add vinegar; cook until evaporated, about 30 seconds.
4. Add hoisin sauce and 1/4 cup water; cook, tossing, until chicken is cooked through, about 1 minute. Remove from heat. Stir in scallion greens and cashews. Serve immediately over white rice, if desired.