In a small saucepan, combine soy sauce, ketchup, Worcestershire sauce, rice vinegar, brown sugar, grated ginger, garlic powder, black pepper, and sesame oil. Stir well to combine. Place the saucepan over medium heat and bring the mixture to a simmer, stirring occasionally.

In a small bowl, mix cornstarch and water until dissolved to create a slurry.

Gradually pour the slurry into the simmering sauce, stirring constantly to prevent lumps from forming. Continue to cook the sauce, stirring frequently, until it thickens to your desired consistency, 3-5 minutes.

Once the sauce has thickened, remove it from the heat and let it cool before using.