In a medium bowl, toss the chicken with the sherry, ginger, and 1½ teaspoons cornstarch; season with coarse salt. Refrigerate for 30 minutes.
Meanwhile, in a small bowl whisk together the chicken broth, soy sauce, rice vinegar, sugar and 2 teaspoons cornstarch. Set aside.
In a large nonstick skillet over medium-high heat, heat 1 tablespoon of vegetable oil. Add half of the chicken and cook until golden brown and cooked through, about 5 minutes. Transfer the chicken to a plate and cover with foil. Add 1 teaspoon of oil to the skillet and cook the remaining chicken (reduce the heat if the chicken is over-browning). Transfer to the covered plate.
In the same skillet, add the remaining teaspoon of vegetable oil. Add the cashews, garlic, and green onion whites. Cook, stirring constantly, until the garlic begins to soften, about 30 seconds. Whisk the sauce again to combine and add to the skillet along with the chicken. Cook until the sauce thickens, about 30 seconds. Serve over rice or noodles and top with the green onion greens.
Chicken: You can substitute skinless, boneless chicken thighs for the breasts.
Serving: Serve over rice or noodles, alongside your favorite vegetables. Classic sides are broccoli, snap peas and water chestnuts.
Sweeten It Up! While not traditional, add fruit such as pineapple, mango, apricots, or orange for more complex flavors.
Make it spicy: Add a sprinkle of red pepper flakes if you like your meals on the spicy side.
Slow Cooker: To make this in a slow cooker, simply brown the chicken in step #3 (it does not need to be cooked the whole way through) and add it to the bottom of a slow cooker. Stir together the sauce ingredients, including the cashews and white parts of the green onion, and pour it over the chicken. Cook on low for 3 to 4 hours. Serve as suggested.
Storing: Keep leftovers in an airtight container in the refrigerator for up to 4 days. Reheat in the microwave or on the stovetop.