A portobello mushroom is a very large cremini, and a cremini is a brown or cream-colored version of the white button mushroom. The flavor of the portobelo mushroom is the same as that of the common supermarket mushroom, except it is more distinct because it is older and more developed. The gills on the underside of the mushroom have progressed to a greater degrees from the pale pink stage at their first break.
Nutritional benefits of portobello mushrooms are many: 1 cup of sliced portobello contains only 42 calories, 1 gram of fat, 5 grams of protein, 3 grams of fiber, and only 12 grams of sodium.
In a large frying pan over medium-high heat, saute mushrooms with some of the olive oil for 2 to 3 minutes or until they are tender. Remove from heat.
Arrange cooked mushrooms evenly in one or two layers in a large baking dish. In a small bowl, combine olive oil, lime juice, garlic, parsley, shallots, white pepper, and salt; pour over mushrooms. In the refrigerator, marinate at least 4 hours or overnight.
Serve either cold or at room temperature. Plate on individual salad plates as an appetizer with 3 slices on the bottom at a diagonal and another 3 slices on top in the opposite direction (makes an appealing diamond pattern). Drizzle some of the marinade over the top, making sure you get some of the shallot and garlic.
* Remove the gills if you desire. The gills are on the undersides of the mushrooms and they connect to the mushroom stems. Because the gills often add an intense brown color to dishes, some cooks prefer to remove them. Use the tip of the small spoon to scrape away the gills. Save the stems and use them when make soup or stock.
Source: Portobello Mushrooms Recipe from the Portobello Cookbook: 40 Quick and Easy Recipes, by Jack Czarnecki. Jack is renowned for his expertise cooking all types of specialty mushrooms.