Bring vinegar to a boil in small saucepan. Reduce heat; simmer 8 to 9 minutes or until reduced to about 2 tablespoons (consistency will be syrupy). Remove from heat; cool.
Heat oil in large nonstick skillet over medium heat until hot. Add mushrooms; cook and stir 5 to 8 minutes or until mushrooms are lightly browned. Add garlic; cook and stir 2 minutes. Add wine; cook 2 to 5 minutes or just until liquid has completely evaporated.
Cooking Tip: When reducing small amounts of liquid, such as the vinegar in step 1 and the wine in step 2, pay close attention to prevent the liquid from burning.
Meanwhile, dissolve cornstarch in broth. Add broth mixture and balsamic reduction to skillet. Bring to a boil. Reduce heat; simmer 15 to 20 minutes or until mixture is reduced by one half. Season with salt and pepper as desired. Remove from heat; stir in butter until melted. Serve immediately.
Nutrition information per serving: 53.3 Calories; 22.5 Calories from fat; 2.5g Total Fat (0.9 g Saturated Fat; 1.3 g Monounsaturated Fat;) 4 mg Cholesterol; 84.2 mg Sodium; 4.1 g Total Carbohydrate; 0.1 g Dietary Fiber; 0.9 g Protein; 0.2 mg Iron; 0.4 mg NE Niacin; 0 mg Vitamin B6; 0 mcg Vitamin B12; 0.1 mg Zinc; 1.3 mcg Selenium; 3.2 mg Choline.