Optional (you can add garlic before the mushrooms and add white wine or marsala or sherry [3 Tbs] when you add the Balsamic vinegar for different flavors
Directions
Melt butter in skillet over medium-high heat.
Add mushrooms and cook until browned and tender (5-10 min)
Stir in vinegar, salt, and pepper. Cook 1-2 more minutes.