4 big Portobello mushroom caps, (optional to trim stems)
4 slices of swiss cheese
4 brioche burger buns, toasted
Mayo (or your choice of burger sauce)
1. In a large bowl, mix together the olive oil, balsamic vinegar, dijon and Weber seasoning. Mix until fully incorporated. Coat each of the four mushrooms with the marinade. Make sure to get some marinade on the gills.
2. Heat a grill pan over medium heat. When the pan is hot, place mushrooms on grill pan with gills facing up. Cook on both sides for 4-5 minutes. When the mushrooms are turned, add cheese and once cheese has melted, remove from pan.
3. Build the burger. Spread mayo on bottom bun, add tomato, lettuce, “burger,” onion and top bun.