Melt butter in a 10-inch skillet over medium-high heat. Add garlic powder and mushrooms; stir fry for 2 minutes. Remove from heat. Add water, wine, onion powder, tarragon and rosemary. Return to heat and bring to a boil.
Meanwhile, mix corn starch and sour cream together in a small bowl. Reduce heat to medium and add sour cream mixture. Simmer 5 minutes or until thoroughly heated. Ladle over meat.