In a medium-sized saucepan over medium heat, combine all ingredients except cornstarch and water. Whisk to combine.
Bring the mixture to a boil, whisking frequently. If you are using it as a marinade only, remove it from heat and allow it to cool to room temperature before use.

To Make a Grilling Sauce:

To thicken the marinade into a grilling sauce, whisk cornstarch and cold water together in a small bowl.
Add the cornstarch mixture to the boiling marinade, whisking to combine. Allow the mixture to boil for 2 to 3 minutes, or until thickened.
Remove from heat and use as desired. Brush onto meats while grilling or serve as a dipping sauce. Enjoy!