PREP AND PREHEAT: Preheat your oven to 400°F (200°C). Line a large, rimmed baking sheet with parchment paper or aluminum foil for effortless cleaning.
MIX THE SAUCE: In a medium bowl, whisk together the soy sauce, hoisin sauce, honey, rice vinegar, sesame oil, minced garlic, and minced ginger. In a separate small cup, mix the cornstarch and cold water until completely smooth, then stir it thoroughly into the main sauce.
PARTIAL BAKE THE CHICKEN: Place your cubed chicken in a separate bowl and toss with exactly half of the prepared stir-fry sauce. Spread the chicken out into an even, single layer on the prepared sheet pan. Bake for 8 to 10 minutes so it begins cooking through and seals in its juices.
ADD VEGETABLES & CASHEWS: Safely remove the hot sheet pan from the oven. Add the broccoli florets, chopped bell peppers, red onions, and whole cashews directly onto the pan alongside the chicken.
COAT AND ROAST: Drizzle the remaining half of the stir-fry sauce over all the newly added vegetables and cashews. Using tongs, toss everything together right on the pan until evenly coated, then spread it back out into a flat, single layer.
ROAST TO PERFECTION: Return the pan to the oven and bake for an additional 12 to 15 minutes. The chicken should reach an internal temperature of 165°F (74°C), the sauce should turn into a thick, sticky glaze, and the vegetables should be beautifully crisp-tender. Serve hot over rice or grains.