Combine the soy sauce, bourbon, chicken broth, brown sugar, ground ginger, onion powder, and red pepper flakes in a mixing bowl and set aside. Cut the chicken into strips about half an inch thick, then into 1-2 inch pieces; place in a bowl and coat thoroughly with cornstarch. Heat olive oil in a large skillet over medium-high heat. Once the oil is hot, add half the chicken, searing one side undisturbed for roughly three minutes before flipping to brown the other side. Remove the cooked chicken to a plate and repeat with the remaining batch. Add a touch more oil to the pan, sauté the minced garlic until fragrant, stirring constantly for under a minute. Pour in the prepared sauce mixture, stirring with a wooden spoon to deglaze any browned bits. Bring the sauce to a boil for about a minute, then return the chicken to the skillet, reduce the heat, and simmer until the sauce thickens and reduces by half while coating the chicken evenly. Serve hot, garnished with chopped green onions alongside rice.