Balsamic Portobello Burger with Caramelized Onions & Side Salad

Directions

1. Slice the onion and cook it in a bit of oil with a pinch of salt in a pan over medium heat until soft and deeply colored, about 15–20 minutes to form caramelized onions.
2. Prepare the mushrooms by removing stems and scraping out the gills. Toss them in a bowl with the marinade and set aside.
3. Whisk together mayo, oil, Dijon, garlic powder, and a pinch of salt to make aioli and set aside.
4. In a skillet over medium-high heat, cook the marinated mushrooms until they are tender, about 3–5 minutes per side. Top with mozzarella and cover until the cheese melts, 2–3 minutes.
5. In the same bowl used for the mushrooms, add the dressing ingredients from the leftover marinade along with honey, oil, Dijon, and salt, then whisk to combine.
6. Tear or chop the romaine and cucumber, and chop half the tomato; add them to a bowl with the dressing and toss to coat. Slice the remaining tomato and reserve.
7. Toast the buns if desired, spread aioli on the bottom buns, layer with lettuce, tomato, the mushroom caps with melted cheese, and caramelized onions, then cap with the top buns.