HEAT 2 tablespoons oil in large skillet over medium heat. Add mushrooms, topside down. Season with salt and pepper. Cover and cook about 6 minutes or until lightly browned. Turn and cook an additional 4 minutes or until fork-tender. Remove from skillet; keep warm.
MELT 1 tablespoon oil in same skillet over medium heat. Remove from heat. Add garlic and Italian seasoning to skillet. Stir 15 seconds. Add vinegar. Return skillet to heat. Cook and stir over medium heat just until mixture begins to thicken, about 1 minute. Turn off heat. Return mushrooms to skillet turning to coat with syrup.
TOAST muffins in toaster. Spread each muffin half with mustard. Top muffin bottoms with lettuce, mushrooms, syrup, tomatoes and muffin tops.
Serving Size (1/4 of recipe), Calories 520 (Calories from Fat 180), Total Fat 20g (Saturated Fat 5g, Trans Fat 0g), Cholesterol 0mg, Sodium 950mg, Total Carbohydrate 72g (Dietary Fiber 6g, Sugars 12g), Protein 13g; Percent Daily Value*: Vitamin A 15%, Vitamin C 10%, Calcium 10%, Iron 20%.
*Percent Daily Values are based on a 2,000 calorie diet.