Preheat oven to 425°F. Spray a medium baking dish with cooking spray (I have used a deep 9-inch by 6-inch dish, a deep 8-inch square dish, and an 11-inch by 7-inch dish, and all work well).
Place chicken in the prepared dish. Sprinkle with cornstarch and toss to coat.
In a separate bowl, whisk together chicken broth, brown sugar, hoisin sauce, sesame oil, salt, garlic, ginger, and red pepper flakes. Pour sauce over chicken and stir to combine.
Bake, uncovered, for 20 minutes. Stir, return to the oven for 5-10 more minutes, or until chicken is cooked through and sauce has thickened.
Remove from oven, stir in peanuts. Season with additional salt and red pepper flakes, to taste. Garnish with sliced green onions, sesame seeds, or extra peanuts just before serving.