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Vegan sliders with portobello and caramelized onion

Vegan Sliders with Portobello Steak

Bite into a delicious Vegan Sliders with Portobello Steak and Caramelized Onions. These vegan sliders are filled with marinated portobello steaks and caramelized onions and topped with fresh arugula and basil aioli for a satisfying quick snack or light meal. 
5 from 2 votes
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Prep Time: 10 minutes
Cook Time: 20 minutes
Marinating Time: 30 minutes
Total Time: 1 hour
Servings: 4 sliders
Calories: 190kcal
Author: Sarah McMinn


Portobello Steaks

Everything Else

  • 1 large white onion, thinly sliced
  • 1 tablespoon olive oil
  • 4 slider buns or ciabatta dinner rolls
  • 1 handful of fresh arugula
  • 1 batch Basil Aoili, recipe follows

Basil Aioli


  • Begin by marinating the portobello. Cut the mushrooms into ½" strips and set aside. Mix together the ingredients for the marinade in a flat, shallow dish. Place the portobello strips in the marinade, submerging them completely. Allow mushrooms to marinate for at least 30 minutes.
  • While the mushrooms marinate, heat one tablespoon of olive oil in a medium sauté pan placed over medium heat. Add sliced onions and reduce heat to low. Saute for 15-20 minutes, stirring frequently, until the onions are golden and caramelized. Remove the onions from heat and set aside.
  • In a small bowl mix together the ingredients for the basil aioli. Place in the refrigerator until ready to use.
  • Transfer the portobellos, along with the marinade, into the hot sauté pan. Turn the heat up to medium-high and bring the liquid to a simmer. Heat until the liquid is absorbed and mushrooms are browned and have reduced in size by about 50%.
  • To assemble the sliders, spread the basil aioli on the bottom side of all four buns. Evenly distribute greens, portobello, and caramelized onions. Top with the other half of the bun and serve immediately.


Serving and Storing - These sliders should be eaten immediately. Leftovers should be stored separately. Store the Portobello Steaks in the refrigerator for up to 3 days. When ready to eat, gently reheat the steaks in the microwave or in a skillet over the stovetop. Store the basil aioli in the refrigerator for up to 5 days.
Recipe Tips
  1. If you are short on time, make the basil aioli in advance. It can be made up to 2 days early. Store it in an airtight container in the refrigerator.
  2. Assemble the sliders as soon as the portobello steaks and caramelized onions are ready. As they cool, they lose their desired taste and texture.
  3. Try these sliders on homemade vegan challah buns. It’s a perfect flavor combination.


Calories: 190kcal | Carbohydrates: 8g | Protein: 2g | Fat: 17g | Saturated Fat: 2g | Sodium: 378mg | Potassium: 208mg | Fiber: 1g | Sugar: 4g | Vitamin C: 3mg | Calcium: 11mg | Iron: 1mg