Simple little concoction I made up the other day. Really good, not too bad on the wallet, vegeterian (for you non-meat types), and it impresses people.
1 pack of fresh portobello tops (Makes 2 sandwiches. Approx $2-4 depending on store and season.
Olive Oil (Extra virgin preferred)
Pepper Jack Cheese
Give the frying pan a good coat of the oil and heat it up. (Set between medium and high on electric stoves)
Add about a 3/4 teaspoon of the garlic and about 1/2 teaspoon of dried parsley and 2 teaspoons of the basil.
Add the mushrooms and cook as you would meat patties. Note that you WILL have to add some oil bit by bit as the mushrooms will absorb it.
They're done when they're darkened all around and a bit shrunken in size. (It only takes about 10 minutes usually)
All you need to do is put the mushrooms on bread or buns, put the cheese on, and voila.
Simple, yummy, fast.