1. Heat small saucepan over medium heat until hot. Add onion, garlic and ginger; cook and stir for 2 to 3 minutes. Add water and sugar; bring to a boil. Cook and stir 13 to 15 minutes or until reduced to 1/2 cup. Remove from heat; carefully stir in soy sauce, vinegar and mustard. Whisk in butter. Serve immediately.