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Portobello Mushroom and Caramelized Onion Sliders

Portobello Mushroom and Caramelized Onion Sliders

These sweet and savory Portobello Mushroom and Caramelized Onion Sliders will have you wanting more! Portobello mushrooms marinated in balsamic vinegar and Dijon mustard with sweet caramelized onions on your favorite bun, what's not to love! 
Course Main Course
Cuisine vegan, gluten free
Keyword portobello mushroom sandwiches, vegan sandwiches
Prep Time 10 minutes
Cook Time 45 minutes
Inactive 1 hour
Total Time 55 minutes
Servings 4 sliders
Calories 329kcal


Portobello Mushrooms

  • ½ cup balsamic vinegar
  • 3 tablespoons Dijon mustard
  • 2 tablespoons olive oil
  • 2 portobello mushrooms
  • Salt

Caramelized Onions

Maple Dijon Mayo


  • Portobello mushrooms: Wipe mushrooms with a damp towel and slice into ½ " slices. Mix balsamic vinegar, Dijon mustard, and olive oil. Marinate the mushrooms for at least an hour.
  • Caramelized onions: Add olive oil to a hot pan. Add sliced onion and cook on medium-low heat for about 35-40 minutes, or until onions are caramelized. Add balsamic vinegar to deglaze the pan. Add salt. Remove onions.
  • Portobello mushrooms: In the same pan that you cooked the onions, place marinated mushrooms and marinade. Cook on medium heat until mushrooms are tender and marinade is cooked down.
  • Maple Dijon Mayo: Mix all ingredients.
  • Slather Maple Dijon Mustard on buns. Add portobello mushrooms and caramelized onions.



Calories: 329kcal | Carbohydrates: 24g | Protein: 2g | Fat: 23g | Saturated Fat: 3g | Cholesterol: 0mg | Sodium: 310mg | Potassium: 362mg | Fiber: 2g | Sugar: 16g | Vitamin C: 5.9mg | Calcium: 49mg | Iron: 0.9mg