Suitable for vegetarians, a portobello burger is a type of burger which uses portobello mushroom caps instead of hamburger patties. Portobellos are large, meaty mushrooms, so a single cap is of comparable size to a meat patty. Although they are sometimes found in restaurants, they are frequently homemade.
Versions of the portobello burger vary widely. The mushrooms are generally marinated before cooking, however. Marinades usually consist of vegetable or olive oil and balsamic vinegar. A variety of spices and other flavorings are also included depending on the version.
Garlic and onions are popular additions to the marinade, and other spices such as thyme, oregano, or basil are also generally included. Salt and pepper are nearly always added to taste as well. Mustard is sometimes also added, and spicier versions may even include jalapeño or chipotle peppers.
Easy to prepare, the marinade ingredients are simply whisked or blended together. Then the mushroom caps are placed in a container with the liquid and allowed to marinate between 15 minutes and two hours. Once complete, the mushrooms are removed and the marinade is reserved and used to baste the portobellos while they cook.
The mushrooms are then placed on a grill or in frying pan and cooked for several minutes on both sides. Many versions place cheese on the mushrooms during the last few minutes of cooking to allow the cheese to melt. Some versions wait to place the cheese until after the mushrooms are removed from the grill.
Hamburger buns or any type of rustic rolls are used to make a portobello burger. The buns may be warmed or toasted first. Additionally, mustard or mayonnaise may be spread onto the buns. Mixing some of the reserved marinade into a portion of mayonnaise and using that as a flavored spread is also an option.
Once the mushrooms are cooked, they are placed on the bottom half of the bun or roll. If the cheese has not been melted onto the mushrooms during cooking it is added now. Cheese choices vary considerably as well, though they are frequently white cheeses. Pepper jack, provolone, Gouda, and even brie are all possible cheese options that would match well with a portobello burger.
In addition to cheese, other toppings are usually included. Similar to traditional a burger, lettuce, sliced tomato, and onions often top a portobello burger. Avocados are also a popular topping for this sandwich. These burgers may be served with the same sides as any hamburger.