Step 1

Combine chicken, 2 tablespoons soy sauce, cornstarch, sherry, and sesame oil in bowl. Combine hoisin, water, vinegar, and remaining 3 tablespoons soy sauce in separate bowl.

Step 2

Heat vegetable oil in 12-inch nonstick skillet over medium heat until shimmering. Add cashews and cook, stirring constantly, until golden brown, 4 to 6 minutes, reducing heat if cashews begin to darken too quickly. Using slotted spoon, transfer cashews to small bowl.

Step 3

Heat oil left in skillet over medium-high heat until just smoking. Add chicken and cook, stirring frequently, until beginning to brown and no longer translucent, about 3 minutes. Add celery, scallion whites, garlic, ginger, and pepper flakes and cook until celery is just beginning to soften, about 2 minutes.

Step 4

Add hoisin mixture, bring to boil, and cook until chicken is cooked through and sauce is thickened, 1 to 3 minutes. Off heat, stir in scallion greens and cashews. Serve.