Recently we prepared portobello mushrooms on the grill a couple of times and we highly recommend this method. It's a meaty, savory, meatless dish that takes a little time in the beginning but is well worth the effort.
Choose big, clean flat mushrooms. Wipe the caps with a damn paper towel. Slice off the stems flush with the cap. Reserve the caps.
Into the gills of the mushroom, insert small wedges of parmesan, garlic, pine nuts, fresh basil and fresh rosemary. Marinate in olive oil and balsalmic vinegar, salt and pepper for 30 minutes.
Grill gill side down for 3 minutes on a high heat then flip and grill another 6 minutes. You can also broil these in your oven. It's amazingly delicious and filling.
Serve with a fresh green salad and roasted potatoes. Along with the potatoes, you can chop the stems and roast with onions and garlic.