Portbello mushrooms are a great meat alternative because they are thick, meaty, and very filling.
Optional: 2 handfuls fresh spinach
Melt butter and garlic until tender. Trim stems off mushrooms and wipe off any dirt with a damp towel. Brush insides of mushrooms with half of melted butter and garlic. peppers, onion, tomatoes, basil, spinach (if desired), olives and black pepper for 3-4 minutes with rest of butter and garlic. Meanwhile, grill mushrooms top up for approximately 4 minutes. Turn over and top with veggie mixture and cheese. Continue grilling until cheese is soft.
Oven option: bake mushrooms for 10 minutes, top with remaining ingredients and cook for another 20-30 minutes or until done.