Begin by dicing the boneless, skinless chicken breasts into 1-inch pieces. In a mixing bowl, coat the chicken pieces with cornstarch, salt, and pepper.

In a large skillet, heat 2 tablespoons of vegetable oil over medium-high heat until shimmering. Carefully add the coated chicken, cooking for approximately 3 minutes on each side until golden brown.

Lower the heat to medium and add minced garlic. Sauté for about 30 seconds until fragrant.

In the same skillet, combine chicken broth, soy sauce, apple juice, ketchup, bourbon, apple cider vinegar, brown sugar, ground ginger, onion powder, and optional crushed red pepper flakes. Stir well and bring to a gentle boil.

Return the browned chicken to the skillet, ensuring it is well-coated with the sauce. Lower the heat and let it simmer uncovered for around 10 minutes.

For a thicker sauce, mix 1 tablespoon of cornstarch with 2 tablespoons of cold water until smooth. Stir this mixture into the sauce and cook for an additional 2 minutes.