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.
Time is flying, friends. Way too fast.
I originally created this recipe over 7 years ago! Somehow I have lived a lifetime in those 7 years but one thing has stayed constant, My Darling Vegan. Well, “constant” is a stretch. The world of food blogging has changed drastically in those 7 years and I am amazed at how quickly it continues to evolve.
But, in an effort to keep up with the changes, I am reviving some of my oldest and best content and making it fresh and new again just for you.
These Vegan Sliders with Portobello Steak and Caramelized Onions were a favorite many years ago. They were one of the first times I discovered the wonders of portobello steak, a meat replacement staple that I now use in my tacos, Philly Cheesesteaks, steak fajitas, and vegan pot roasts.
Since I’ve come to love portobello steak so so much, I decided it was time to revisit these delicious portobello sliders.
Ingredients & Substitutions
These portobello sliders are made with smoky marinated portobello steaks, sweet caramelized onions, and basil aioli all inside a ciabatta slider bun. Sweet, savory, and oh so good!
Here is everything you’ll need.
- Slider Buns – This recipe calls for ciabatta slider buns but any dinner roll or slider bun will do. I love using this challah recipe for sliders.
- Caramelized Onions – For this, you will need one large white onion and 1 tablespoon of olive oil.
- Portobello Steaks – These juicy portobello steaks require 5 simple ingredients: white cooking wine, balsamic vinegar, garlic powder, olive oil, salt.
- Basil Aioli – A combination of vegan mayonnaise, garlic, and fresh basil.
- Fresh Arugula – Feel free to swap out with fresh spinach or mixed greens.
Disclosure: This post may contain affiliate links.
Step-by-Step Instructions
Step One – Make the Portobello Steaks
These sliders start with a base of portobello steaks. Portobello steaks are juicy, meaty, delicious, and SUPER EASY to make!
To begin, whisk together the ingredients for the marinade in a shallow dish and set aside. Next, clean the mushrooms with a damp kitchen towel to remove any soil that clings to the mushrooms. Cut the mushrooms into 1/2″ slices. Place the mushroom slices in the shallow baking dish or a large Ziplock bag and marinate for about 30 minutes, flipping halfway through.
To cook the mushroom steak, transfer the portobellos, along with the marinade, into a hot sauté pan placed over medium-high heat. Bring the liquid to a simmer. Heat until the liquid is absorbed and mushrooms are browned and have reduced in size by about 50%.
Step Two – Make the Caramelized Onions
Caramelized onions take a little bit of time, but they are so worth it. The caramelization process slowly pulls out the natural flavors of the onion, making them intensely sweet and flavorful.
To make caramelized onions, first coat the bottom of a heavy-bottomed sauté pan with olive oil. Heat it over medium-low heat and add the sliced onions. Cook the onions slowly, stirring them every few minutes. After 10 minutes, sprinkle with a pinch of salt and continue to cook for another 10-20 minutes until onions have reduced in size and are caramel in color.
Step Three – Assemble the Sliders
Whip together a batch of Basil Aioli. I do this by hand but if you want a smoother spread, you can whip this up in a blender.
To assemble the sandwiches, place a handful of fresh arugula on the bottom of each bun. Top with portobello slices and caramelized onions. Spread a generous amount of Basil Aioli on your bun and place it on the top.
Serving and Storing
Serving – These sliders should be eaten immediately.
Storing – Store leftovers 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.
Tips and Tricks
- 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.
- Assemble the sliders as soon as the portobello steaks and caramelized onions are ready. As they cool, they lose their desired taste and texture.
- Try these sliders on homemade vegan challah buns. It’s a perfect flavor combination.
Frequently Asked Questions
Yes! You can use any mushroom of choice. I also recommend jackfruit. To use jackfruit, marinated it for 39 minutes before sautéing it in a hot pan for 3-5 minutes.
I often use ciabatta rolls for my sliders. You can also make homemade challah buns or use any bun or roll of your choice.
The portobellos can marinate for up to 24 hours in advance. You can also make the aioli up to 2 days in advance. However, do not heat or assemble until you are ready to serve.
More Vegan Slider Recipes
- Jackfruit “Pulled Pork” Sliders w/ Mango Salsa
- Vegan Southwest Sliders
- Tofu Banh mi Sliders
- Vegan Black Bean Burger
- Zesty Black Bean Sliders
Vegan Sliders with Portobello Steak
Ingredients
Portobello Steaks
- 2 large portobello mushrooms, thinly sliced
- 1/4 cup white cooking wine
- 2 tbsp. balsamic vinegar
- 1/2 tsp. garlic powder
- 1 tbsp. olive oil
- 1/2 tsp salt
Everything Else
- 1 large white onion, thinly sliced
- 1 tbsp. olive oil
- 4 slider buns or ciabatta dinner rolls
- 1 handful of fresh arugula
- 1 batch Basil Aoili, recipe follows
Basil Aioli
- 1/4 cup vegan mayonnaise
- 2-3 cloves garlic, minced
- 5-6 fresh basil leaves, minced
Instructions
- Begin by marinating the portobello. Cut the mushrooms into 1/2" 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.
Notes
- 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.
- Assemble the sliders as soon as the portobello steaks and caramelized onions are ready. As they cool, they lose their desired taste and texture.
- Try these sliders on homemade vegan challah buns. It’s a perfect flavor combination.
Hi, I’m Sarah. I’m a 14-year (and counting) vegan, professionally trained photographer, former pastry chef, founder of My Darling Vegan, and author of the
Lauren says
This is a delicious perfect recipe. I have made it as is twice . Tonight we are having the mushrooms and onions over mashed potatoes with the marinade as a gravy (thickened up with a roux). My meat-loving sister even improvised a version that includes steak but as far as I’m concerned the meat would be an unnecessary distraction.
Sue says
This was so simple, yet so delicious. Thanks Sarah!
elizabeth says
These sound so good, I am thinking of making them for a party i have coming up. Could i make these ahead? If so, what would be the best way to re-heat them? Or, could I possibly bake them instead if sauteeing?
Sarah says
You could make all the parts ahead of time, but I wouldn’t recommend assembling the sandwiches until shortly before the party. You could bake the mushrooms and onions rather than saute them, or saute and then keep in a lowly heated oven until you’re ready to assemble.
Bellaisa says
I have been a vegetarian pretty much my whole life, and I never really felt the need to have a ‘meat’ substitute for burgers. I ate a burger with some vegetables, cheese, and condiments till I was in my 30’s, but once we tried a portebello mushroom in there – I’ve never gone back. For anyone who is wondering whether or not it will taste good, take it from one of the pickiest people around (me), this is going to be a good burger!
Sarah says
Thanks Bellaisa! There’s nothing quite like a portobello, is there?
Greg says
You have “1tbs olive oil” listed twice under marinade. Did you mean Worcestershire for one of those? If so, it worked like a charm! I love this recipe. Thank you !
asim saeed says
I will def try this,
But let me recommend my version
Everything is the same, except
I make a dill alioli, use Fresh dill, mayo, garlic powder, and lemon juice, with salt, pepper is okay
Instead of caramelized onion, try fresh pickled onions.. Thin slice red onions, and soak in vinegar with a dash of salt for about minimum 20 mins
And I top it all off with some fresh arugala
Trust me you will love it
Sarah says
Thanks for sharing the recipe. It sounds delicious!
Mushrooms Canada says
Fantastic little burgers!! You can never go wrong with juicy portabella’s and caramelized onions…thanks for sharing this little treat!!
-Shannon
Renard Moreau says
[ Smiles ] It is hard to say, “No,” to a delicious vegan burger.
I appreciate the fact that you posted this nice, easy to follow vegan recipe.
Amy says
This looks absolutely delicious!!! I think your burgers will be my dinner tomorrow! What’s better to start the week with than portobello burgers? 🙂
Emanuelle says
Looks absolutely delicious! The perfect vegetarian meal!!
jen l p says
This was delicious. I didn’t have white wine, so I used red. It turned out fine. Great recipe!
Thess says
mmm, looks delicious!! I am absolutely a sandwich fan! I love my vegan breadrolls with nuts and seeds together with hummus, avocado and tomatoes. Yummy:) I will definitely try this version though, looks amazing!!
Johanna says
My local meat-packers Grille serves a wrap with BBQ tempeh, potatoes, and carrots. I get the sauerkraut instead of the coleslaw. I tempeh/tofu reuben is, therefore, also very pleasing to me. I love sauerkraut!
Sarah says
sounds amazing!