Portabella mushrooms on the grill, which I have done many times before. I'm not a vegetarian, but I love these myself, and make them pretty often. Marinate large caps in balsamic vinegar, garlic, chopped rosemary, olive oil. salt and pepper. Grill, and serve on a toasted bun with melted cheese (I like swiss, mozz or jack), slabs of roasted red pepper, romaine lettuce or arugula, mayo. Sorry, no clever ideas for smoking...yet.