Portabello Burger

Ingredients

• 1/2 cup olive oil (approx.)
• 3 dashes balsamic vinegar (approx.)
• 1 handful rosemary, thyme, basil, or sage (depending on what we happen to have on hand)
• 2-3 cloves minced
• 1 pinch salt and pepper
• 2 portabello mushrooms
• 1 onion, diced
• 1 pat butter
• 1 handful sundried tomatoes, cut into smallish pieces(optional)
• 2 good sandwich bread (we like par-baked sandwich rolls from Trader Joe's or Fresh Direct)