Start by cutting up the chicken thighs into bite-sized pieces and placing them in a zippered top, gallon-sized plastic bag.
Next, add 2 tablespoons of cornstarch, kosher salt, pepper, onion powder, and garlic powder.
Then zip the bag closed and shake the ingredients around until the chicken is well coated.
Over medium heat, heat a large skillet on the stove. Then add half of the oil. Once it's hot, sear the chicken in 2 batches, working until cooked through. Place the cooked chicken on a plate and add another tablespoon of oil to the pan and repeat with the remaining chicken.
Add the garlic directly to the skillet and cook for about 30 seconds, or until just fragrant. Add in the apple juice, chicken stock, bourbon, and soy sauce and stir to combine.
Add the brown sugar and ground ginger to the skillet and stir to combine.
Whisk together the water and remaining 2 tablespoons of cornstarch until dissolved in a small mixing bowl. Slowly pour in the cornstarch slurry while whisking it in until combined.
Then, add the chicken back to the skillet and coat in the sauce.
Finally, bring it to a simmer and simmer for 2 minutes stirring occasionally. Take off the heat and add scallions if desired.