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?
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I have been wanting to make a portobello mushroom sandwich for the blog for a while now. These Portobello Mushroom and Caramelized Onion Sliders are finally getting a debut because I was on a sandwich-making kick recently.
I fell in love with portobello mushroom sandwiches on my first trip with my husband. This was quite a few years before I knew I was gluten intolerant so there were more options for me eating out.
On the trip I had three vegan portobello mushroom sandwiches at three different restaurants because they looked like the best choice on each of the menus.
I was happy with every single one of them and not at all tired of eating the same thing several times on the trip.
The ingredients that add a ton of flavor to the mushrooms are balsamic vinegar and Dijon mustard.
Not only are the mushrooms marinated in balsamic vinegar and Dijon mustard, but they are also cooked down in the marinade as well.
You may taste the mushrooms and think that the flavors are quite strong, but once you combine them with your favorite buns and some sweet caramelized onions, you will taste the symphony of flavors that the mushrooms become part of.
Caramelized onions are one of those ingredients that elevate anything that you add them to. In fact, I would recommend doubling the amount so that you can use them in other dishes.
Tips
- For caramelized onions you need some patience. It takes a good 40 minutes to get nicely browned onions. Slow and steady wins the race.
- If the onions start to stick, add a little water, like a quarter of a cup or so.
- Balsamic vinegar adds a wonderful flavor to caramelized onions. I always add a couple of splashes near the end of the cooking time.
- Make a double batch of the caramelized onions and add them to a Vegan Caramelized Onion and Mushroom Grilled Cheese, a baked potato, or Vegan Mashed Cauliflower with Caramelized Onions and Mushrooms.
- Make a double batch of the whole recipe and add half of it to pasta with the Maple Dijon Mayo and some steamed asparagus.
- Cook mushrooms in marinade for more intense flavor.
- The type of bread / buns that you use makes a big difference in the overall taste of the sandwiches.
Other Vegan Sandwiches
The combination of flavors in these vegan portobello mushroom sliders is rich and satisfying. If you love this recipe, please come back and leave your feedback and star rating.
📋 Recipe
Portobello Mushroom and Caramelized Onion Sliders
Ingredients
Portobello Mushrooms
- ½ cup balsamic vinegar
- 3 tablespoons Dijon mustard
- 2 tablespoons olive oil
- 2 portobello mushrooms
- Salt
Caramelized Onions
- 2 cups sliced onion
- 2 tablespoons olive oil
- 2 tablespoons balsamic vinegar
- Salt
Maple Dijon Mayo
- ¼ cup vegan mayo
- 2 tablespoons Dijon mustard
- 2 tablespoons maple syrup
- Buns - I used Pamela's gluten free pizza mix
Instructions
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
- 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.
- 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.
Nutrition
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*Note: Nutrition information should be considered an estimate only. Different nutrition calculators give you different results. Also note that the buns were not calculated into the nutrition info.
Caroline says
I was never a huge mushroom fan but WOW. I loved this recipe so much. It’s so fantastic! Each part - from the onions to the sauce - goes beautifully together. Sharing this recipe!!!
Willow Moon says
Thanks so much Caroline! I'm actually not a big mushroom fan either!
Wendy says
Fantastic meal for meatless Monday.
Made as written except I made a basil mayo.
Served in brioche rolls. Such a nice change,
thanks for the recipe!
Willow Moon says
Thanks Wendy, I'm glad that you liked it! Basil mayo with this sounds delicious!
Amy Paul says
OH. MY. GOD.
You weren’t exaggerating when you said tasting the shrooms may seem strong, but combined with the other ingredients it all comes together in the most delicious sweet and savory mouthfeel. My new favorite sandwich, Willow, hats off to you.
Willow Moon says
Thanks so much Amy! I’m so glad you liked it!
Terri says
Can you send me the bun recipe you used? I can’t find the vegan/gluten free recipe using the pizza crust mix on the Pamela’s website? I would like to make these mushroom sliders with the buns you used as well. Thanks!
Willow Moon says
Sure! If you ever want to check out other recipes on their site: I went to their recipe section, then I scroll down on the left hand side to the product and click pizza mix. For this recipe I used the Crusty Seedy Dinner Rolls (click for recipe). They have a ton of ways to use their products, which is really cool when you need a vegan gluten free recipe!
mcordelia says
Loved these!! Will make this recipe again!
Willow Moon says
Thanks, that makes me so happy!
Carolyn McDonald says
Had to try these since they looked and sounded so delicious! I followed the recipe exactly and found the sandwiches to be way too sour from the amount balsamic vinegar. There is definitely potential here but I would need to adjust the recipe to have these again.
Willow Moon says
I’m sorry that you didn’t like them Carolyn. Hopefully you at least had them on some good bread or buns to mellow out the flavor. As I said in the post the mushrooms are quite strong and need good buns, the caramelized onions, and the Maple Dijon Mayo to create a balance of flavors. If the mushrooms were mellow they would get lost in the sandwich.
Christy says
I stumbled upon these when trying to find a yummy recipe to take to a carnivore party. 😉 There were none left. We make these at least twice a month now and most of the time we just toast some organic bread and use that for the bun.
So yummy and delicious! Thanks for such an incredible recipe!
Willow Moon says
Thanks Christy! That makes me so happy!
Mary says
This sounds amazing !
Did your nutritional info include your Pamela bun?
Willow Moon says
Yes, but keep in mind it is an estimate.
Lisa says
Under nutrition in notes it says did not include buns, but here you said it does? Trying to figure out approx calories without the bun.
Willow Moon says
Sorry about that Lisa. I just commented again. The recipe does NOT have the buns in the calculation. I went into the recipe card to double check.
lisa says
Thanks. I made last night and carmalized the onions. They were awesome
Willow Moon says
I'm so glad you liked it!
Willow Moon says
Correction: Sorry, I first posted that it did and that it was an estimate, but it does not have the buns in the calculation.
Maria Koutsogiannis says
YUM! These look amazing. Definitely going to try these!
Kate Taylor says
What gluten free buns are those!? Did you make them?
Willow Moon says
They are using Pamela's pizza mix. They are delicious! Check out their website - they have all sorts of recipes with their products.