Equipment
Ingredients
Mushrooms & Marinade
- 4 large portobello mushrooms, stems removed, gills scraped clean if desired
- 45 ml balsamic vinegar
- 45 ml olive oil
- 15 ml soy sauce
- 2 garlic, minced
- 2 g dried thyme
Assembly
- 120 g gruyère cheese, sliced or grated
- 4 burger buns, split
- ½ red onion, thinly sliced rings
- 1 tomato, sliced
- 4 lettuce leaves, washed and dried
- 60 ml mayonnaise
Nutrition (per serving)
Method
Wipe the mushroom caps clean with a damp paper towel. Whisk together balsamic vinegar, olive oil, soy sauce, minced garlic, and thyme in a small bowl.
Brush the marinade generously over both sides of the mushroom caps. Let them sit at room temperature for 15 minutes to absorb the flavors.
Preheat your grill or grill pan to medium-high heat (approx. 200°C/400°F).
Grill the mushrooms cap-side down first for 4-5 minutes until grill marks appear and they begin to soften.
Flip the mushrooms. Top each cap with the sliced Gruyère cheese. Cover the grill (or pan) with a lid to help the cheese melt, cooking for another 3-4 minutes.
While the cheese melts, place the split buns on the cooler side of the grill to toast until golden brown, about 1-2 minutes.
Spread mayonnaise on the toasted buns. Layer the bottom bun with lettuce, tomato, the cheesy mushroom cap, and red onion. Cap with the top bun and serve immediately.
Chef's Notes
- Scraping the black gills out with a spoon before marinating removes potential bitterness and prevents the burger from dripping dark liquid, though it is not strictly necessary.
- Gruyère has a distinct nuttiness that pairs perfectly with the earthiness of mushrooms. If unavailable, Swiss cheese or sharp white cheddar are decent substitutes.
- For a better crust, place a heavy pan or burger press on top of the mushrooms during the first few minutes of grilling.
- Ensure your grill is properly preheated; a low temperature will cause the mushrooms to steam in their own juices rather than sear.
Storage
Refrigerator: 2 days — Store components separately. Reheat mushrooms gently.
