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Juicy Portobello Burgers with Vegan Blue Cheese & Caramelized Onions

These juicy portobello burgers with vegan blue cheese & caramelized onions are perfect for summer grilling. Portobello mushrooms are marinated in a zippy mixture of balsamic vinegar, tahini, olive oil, shallots, garlic, and chives for just 30 minutes (or more if it suits your fancy). Then, they're grilled until tender, nestled between crusty bread, and topped with caramelized onions + a heaping dollop of vegan blue cheese.
Prep Time30 mins
Cook Time25 mins
Total Time55 mins
Course: Burger, Sandwich
Cuisine: plant-based, Vegan
Servings: 2


Portobello Mushrooms

  • 2 medium or large portobello mushrooms, washed
  • cup balsamic vinegar
  • 4 tablespoons chopped fresh chives
  • 2 tablespoons minced shallots
  • 2 tablespoons olive oil
  • 1 tablespoon tahini
  • 1 clove garlic, minced
  • ¼ teaspoon sea salt
  • Freshly ground black pepper, to taste

Vegan Blue Cheese

  • cup hemp seeds
  • ¼ cup plain, unsweetened almond milk
  • 2 ½ tablespoons white wine vinegar
  • 1 ½ tablespoons fresh lemon juice
  • 1 teaspoon nutritional yeast
  • ½ teaspoon garlic powder
  • ½ teaspoon tahini
  • ½ teaspoon sea salt
  • ½ block firm or extra firm tofu (I use sprouted tofu)

Caramelized Onions

  • 1 red onion, sliced into ¼-inch thick rings
  • 1 tablespoon coconut oil
  • ½ tablespoon agave nectar

Additional Ingredients + Garnishes

  • 2 hearty burger buns (gluten-free if you prefer), toasted
  • Sprouts
  • Peppery greens


For the Portobellos

  • Remove the stems of the portobellos. Then, use a spoon to scoop out the gills and discard. Add both portobellos to a large ziploc bag or container.
  • Add the balsamic, chives, shallots, olive oil, tahini, garlic, salt, and pepper to a bowl and whisk together. Pour the marinade into the bag and toss to coat the mushrooms.
  • Let the mushrooms marinate for at least 30 minutes, tossing every 10-15 minutes.
  • Heat a grill pan or grill over high heat. Place the mushrooms on the grill and grill for 5-6 minutes on each side. Remove from grill and let cool slightly.

For the Blue Cheese

  • While the mushrooms marinate, make the blue cheese by adding the hemp seeds, almond milk, white wine vinegar, lemon juice, nutritional yeast, garlic powder, tahini, and sea salt to a blender. Blend on high for 2 minutes.
  • While the mixture is blending, crumble the tofu in a bowl.
  • Pour the hemp seed mixture over the tofu and toss to coat. Refrigerate until ready to use.

For the Caramelized Onions

  • Melt coconut oil in a skillet over medium heat. Add in the onions and agave nectar and cook for 10-15 minutes or until caramelized, stirring occasionally.

To Assemble the Burgers

  • Place a portobello on each bun, top with caramelized onions, blue cheese, and sprouts. Serve immediately.