This satisfying veggie sandwich is stacked high with marinated mushrooms, caramelized onions, roasted beets, goat cheese, and crisp veggies. Because who said vegetarian sandwiches had to be boring?!
Marinate Mushrooms: Add the sliced mushrooms to a medium bowl. Pour balsamic vinegar and tamari over top. Toss to coat. Set aside.
Caramelize Onions: Meanwhile, melt butter in a skillet over medium heat. Add onions and cook, stirring frequently, until soft and golden brown, 20 to 25 minutes. If the onions start to stick while cooking, add a splash or two of water. Pour in the balsamic vinegar and cook until the liquid is absorbed into the onions, about 2 minutes. Remove onions from pan and set aside.
Cook mushrooms: Return the skillet to medium-high heat. Scatter in the mushrooms and the marinade. Sauté the mushrooms until soft, 3 to 5 minutes(if the mushrooms start to stick, add a bit of oil).
Assemble: For each sandwich, spread the white bean dip and goat cheese on the inside pieces of bread. Layer the beets, lettuce, tomatoes, mushrooms, and caramelized onions. Brush a bit of butter on the exterior of the sandwich (both sides) and place in the skillet over low heat. Cook on both sides until golden brown, about 2 minutes per side.
Notes
Roasting beets: Wrap the trimmed beet in foil. Bake at 400°F (200°C) until fork-tender, about 45 minutes. Once cool enough to handle, peel and use as directed. Cooked beets can be refrigerated for 3 to 4 days.
Meal prep idea: Make a double batch of mushrooms, beets, and caramelized onions. That way, you can quickly assemble delicious sandwiches throughout the week.