Several years ago, my dear friend the Free Market Mommy made portobello sandwiches for dinner one night when I was visiting--so delish! And very easy. So, I'm going to give a general outline of how to create your own.
portobello mushrooms (1 per person)
cheese slices (1 per mushroom. I recommend provolone)
olive or veg oil
bread or buns (I used multigrain toast, but they're also tasty on hamburger buns)
mustard (I used creole, but you can use your favorite)
salt and pepper
What to do.
Use a spoon to remove the stems and gills from the portobellos. Heat a skillet over medium-high heat, with enough oil to coat the bottom. (Or use a grill pan, ora real grill, or a George Foreman grill--you get the idea.) Cook the mushrooms for a few minutes per side, seasoning with salt and pepper once they are cooked (the salt will draw out a lot of juices, so they will cook faster if you salt them after cooking instead of before). Once they're about ready, top each with a slice of cheese (the provolone works well because the slices are round, like the mushrooms) and heat until melted. (You can cover the pan to speed the melting.) If you're using sandwich bread, toast it. spread one slice with mayo & mustard, top with a lettuce leaf, and your cheesy 'shroom. Top with the other slice of bread, cut it in half, and enjoy your sammie!