Trim any fat from the chicken breasts and cut them into 1-inch pieces. In a medium bowl, mix together 4 tablespoons of the cornstarch with the salt and pepper. Add the chicken and toss to coat evenly.

In a large skillet or pot, heat half of the oil over medium-high heat. Once hot, add half of the chicken pieces and cook without stirring for 3 minutes. Flip each piece and cook for an additional 3 minutes.

Remove the cooked chicken from the skillet and set aside. Repeat with the remaining oil and chicken.

Add the minced garlic to the skillet and sauté for 20-30 seconds until fragrant.

Add the water, soy sauce, apple juice, chicken broth, ketchup, bourbon, vinegar, brown sugar, ground ginger, onion powder, and red pepper flakes. Stir well and bring to a boil over medium-high heat.

Reduce the heat to low and return the chicken to the skillet. Simmer for 10-15 minutes, stirring occasionally, until the sauce thickens and coats the back of a spoon.

In a small bowl, mix the remaining 1 tablespoon of cornstarch with 1-2 tablespoons of water to create a slurry. Stir into the sauce to thicken further if desired.

Serve hot over steamed rice.