Oh my goodness this was amazing!
Mix two parts EVOO to one part balsamic vinegar. Chop up a garlic clove or too Sprinkle thyme, pepper and a dash of salt into vinegar and EVOO mixture. Whisk to mix ingredients and brush over underside of mushroom caps. Toss in a 425 degree oven for about 20 and boom! You've got an awesome meal. Use the extra juice from the pan for dressing.
I put it over spinach leaves and a bunch of raw veggies I had in the fridge.