Prepare the Chicken. In a bowl, coat the chicken pieces with cornstarch until evenly coated. This will create a crispy texture when cooked.
Make the Firecracker Sauce. In a separate bowl, whisk together the brown sugar, hot sauce, soy sauce, minced garlic, red pepper flakes, and water. Set the sauce aside.
Cook the Chicken. In a large skillet or frying pan, heat the vegetable oil over medium-high heat. Add the coated chicken pieces and cook until they are golden brown and cooked through, about 5-7 minutes per side. Remove the chicken from the pan and set it aside.
Finish the Dish. In the same pan, add the Firecracker Sauce mixture. Bring the sauce to a simmer and cook for about 2-3 minutes, or until it thickens slightly. Return the cooked chicken to the pan and toss it in the sauce until the chicken is well coated.
Serve and Garnish. Transfer the Firecracker Chicken to a serving platter. Garnish with diced green onions for a fresh burst of color and flavor.