Take the stems off from the mushrooms, and save for another time.
Wash mushrooms and set in a colander to dry.
Whisk all of the marinade ingredients together in a very large bowl.
One at a time, dip the whole mushrooms in the marinade, making sure to coat the entire mushroom. Set aside and do this to the remaining 3 mushrooms.
Place all 4 mushrooms back on the bowl and cover with a lid. Let mushrooms marinate for at least 1 hour.
Heat a large nonstick skillet over medium / low heat.
Place the mushrooms in the pan face down and place a lid on top.
Cook for 3 minutes, flip the mushrooms, add 1/4 cup of water to the pan and place the lid back on.
Steam the mushrooms for another 2 minutes and then flip them one more time, add a bit more water and steam them for 2 additional minutes. (you can flip them more often if you want and you can add a bit more water if all of the water evaporates. As long as they are cooked for 7 minutes and neither side gets burned, your good!)
See HappyCow recipe for "Beet, Fennel, Lime Pate" (category: dips).
Assemble using burger buns, sprouted bread, or stack it on romaine leaves for a gluten free option.

4 Portobello Mushrooms
Marinade:
1/4 cup plus 1 tablespoon olive oil
2 tablespoon soy sauce
2 teaspoon balsamic vinegar
2 teaspoon sugar
Juice from half a lime
1 clove garlic, grated