If you're looking for an easy but delicious meal, especially for vegetarians or vegans, then mushroom sandwiches might be worth considering. The rich flavor and meaty texture of mushrooms makes them a great burger substitute, without the deservedly bad reputation that accompanies many types of veggie burgers.
Choose your mushrooms. Large portabella caps are ideal, because one mushroom is often about the size of a hamburger roll. If you can't find portabellas (or prefer a cheaper option), consider criminis, which are a smaller version of the same flavorful mushroom. If the only mushrooms you can get are the standard white kind, don't despair. They will make a fine sandwich too.
Wash and prepare your mushrooms. If you will be using portabellas, just wash them gently and remove the stems. For smaller mushrooms, rinse them and chop into chunky pieces.
Season the mushrooms. Brush olive oil over portabellas, or stir a tablespoon or so of oil into your bowl of mushroom chunks. Drizzle on a bit of balsamic vinegar and sprinkle generously with salt.
Cook the mushrooms. Large mushrooms prepared in this way are great for grilling. Large or small mushrooms can also be sauteed or baked in a pan in a 350 degree oven. Cook the mushrooms until they have released their juices and become tender. The length of time that this will take will vary a lot depending on your method of cooking and the size of your mushrooms.
Assemble the mushroom sandwiches. Use one large cap for each sandwich, or use a slotted spoon to scoop mushroom pieces onto your rolls. Most toppings that are good on burgers could also be used on mushroom sandwiches, for example, cheese, ketchup, mustard, relish, onion, lettuce, or tomato could be delicious, depending on your personal preference.