Grilled portobello mushroom burgers make for a tasty vegetarian meal. To maximize the flavor, clean and marinate the mushroom caps in a tangy balsamic vinegar mixture before it hits the barbecue. Add your favorite toppings like tomatoes, lettuce, or onions for the ultimate veggie burgers.
Portobello mushroom burgers will impress even the most devoted meat lover. Mushrooms have incredible umami and natural meaty flavors when cooked. The size and thickness of the caps are perfect to grill and they fit nicely inside toasted burger buns.
There are a few key preparation steps to make. The gills or brown stuff underneath the cap must be scraped out. The cleaned caps then briefly marinate in a balsamic vinegar and soy sauce mixture. Grilling both sides of the caps tenderizes the mushrooms while adding a smoky charred texture to the surface.
How to make portobello mushroom burgers
- Prep the mushrooms by removing the stem and gills.
- Score a crosshatch pattern on the mushroom cap.
- Marinate the mushrooms in a large bowl with the vinegar mixture for 30 to 60 minutes.
- Preheat the grill over medium-high heat.
- Grill mushrooms cap side down, until grill marks appear, 4 to 6 minutes.
- Flip and cook covered until tender, 3 to 5 minutes. Add cheese during this step if using.
- Transfer grilled mushrooms to toasted buns and add desired toppings.
Preparing the mushrooms
The key to undeniably delicious mushroom patties is to properly clean and prepare the caps. The stems and brown gills under the cap need to be first removed. Simply trim off the stem and use a large spoon to scoop out the gills.
The brown sections will easily lift off, this is especially important because it can give the mushrooms a muddy flavor. Clean the tops with a damp cloth to remove any dirt.
Score the top for better texture
The outer surface of the large mushroom cap can become chewy when cooked. In order to tenderize and make it easier to chew, create a shallow cross-hatched pattern on top to help break up the skin. A bonus is that more of the marinade gets infused into the mushroom beneath that thicker top layer.
Marinate the mushrooms
Mushrooms already have a ton of natural umami flavor coming from glutamic acid and nucleotides that enhance the taste. However, a brief 30-minute soak bumps up the taste-factor to absolutely delicious.
To make an imitation beef burger, a mixture of balsamic vinegar, soy sauce, olive oil, garlic, salt, and pepper coat the fungi. The process works just like marinating meat and poultry before grilling.
The right way to grill
The goal is to get a lightly charred portobello mushroom that’s also tender and juicy. Start by placing the vegetable with the gill-side facing up. You’ll get nice brown marks on the back, but this also allows the juices to stay in the cup-shaped cap.
While the moisture is released, the marinade continues to infuse into the mushroom. Flip the cap to finish cooking the other side. This allows most of the moisture to evaporate so the burger is not soggy when added to the toasted bread.
- Homemade mayonnaise or aioli
- Pesto sauce
- Sharp cheddar, swiss cheese, or fresh mozzarella
- Sliced avocado
- Ripes tomatoes like beefsteak
- Crisp and tender types of lettuce like butter leaf
- Roasted red peppers
Can mushrooms be washed?
You can gently rinse mushroom caps as they are covered with a water-repelling protein called hydrophobins. The issue is when the exposed gills underneath get exposed to water, they act like a sponge soaking up moisture and this creates a soggy product. That’s why mushrooms should never be soaked in water, especially portobellos.
Grilled Portobello Mushroom Burger
- 4 portobello mushrooms, 4 to 5 inches in diameter, with stems and gills removed
- ⅓ cup (79 ml) extra-virgin olive oil
- 3 tablespoon (45 ml) balsamic vinegar
- 1 tablespoon (15 ml) soy sauce
- 1 tablespoon (10 g) minced garlic
- 1 teaspoon (6 g) kosher salt
- ½ teaspoon black pepper
- 4 burger buns
- Prepare the mushrooms by cutting off the stems, then use a spoon to scoop out the brown gills. Use a damp paper towel to gently clean any dirt off the surface.
- Use the tip of a paring knife to cut a ½-inch crosshatch pattern on the tops of the mushroom caps, about 1/16-inch deep scores.
- In a small bowl whisk together olive oil, vinegar, soy sauce, minced garlic, salt, and pepper.
- Add mushrooms to a large plastic bag or baking dish. Turn to coat in the marinade and allow to sit for 30 to 60 minutes.
- Preheat grill over medium-high heat 350 to 400ºF (177 to 204ºC).
- Clean the grill and then carefully grease the cooking grates with tongs and a paper towel dipped in oil.
- Remove the mushroom from the marinade then place on the hot grill, cap-side down.
- Cover and cook until mushrooms have released their liquid with charred marks, 4 to 6 minutes.
- Flip and cook covered for 3 to 5 minutes.
- If adding cheese place it on after flipping, cover and cook until melted.
- Place the grilled portobellos on toasted burger buns and add desired toppings.