Cut the chicken breasts into bite-sized pieces.
Mix bourbon, soy sauce, brown sugar, garlic, ginger, and black pepper in a bowl.
Heat vegetable oil in a large skillet over medium-high heat.
Add chicken and cook until browned, about 5-7 minutes.
Pour the bourbon mixture over the chicken.
Bring to a simmer and allow to thicken.
Mix cornstarch with water and add to the skillet.
Cook for another 2-3 minutes until sauce thickens.
Serve hot, garnished with chopped green onions.