Spritz non stick fry/saute pan with olive oil. Saute shallots/onions for 2 minutes. Add Garlic and saute for 1 more minute.
Add Portobello mushrooms, Balsamic vinegar, thyme ( this is Great with fresh thyme) and basil. Lower heat and cover pan.
Cook for 7-12 minutes until mushrooms have turned a brownish color and become flexible. If the pan gets dry you can add a splash of water, broth, or red wine.