Melt butter in medium saucepan on medium heat. Add onion; cook and stir 3 minutes or until tender.
Stir in Gravy Mix, thyme and water with whisk until well blended. Stirring frequently, cook on medium heat until gravy comes to boil. Reduce heat to low; simmer 1 minute or until thickened, stirring occasionally. (Gravy will continue to thicken upon standing.)