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Portabella mushroom and caramelized onion slider sandwich

A Simple Life is its own Reward.

Just like this simple baby portabella mushroom slider sandwich.

The meaty portobellos are often regarded as alternative to steak burger, much to the delight of vegetarians. Both in taste and texture these baby bellas can make any carnivore hungry for more.

baby portabella mushrooms

I have tried so far just four or five variety of mushrooms like porcini, crimini, shitake and enoki, portobello remains my favourite for its sheer versatility. You can stuff them with anything that fancy you, grilled them, roast them or pan-fried them they are bound to come out as winner in every case.

Cleaning the mushrooms : Mushrooms are dirty unless your supermarket stocks jet-sprayed clean mushrooms. So rinse them well under cold running water. I use one tiny vegetable brush to clean the surfaces of the mushrooms. You can use any old toothbrushes too to clean it. Unlike the bigger version of portobello mushrooms baby bellas do not have those woody stems. If your mushrooms has got woody stems then it will be better to use the head or cap of the mushroom.

Tips : Do not discard the woody stems altogether. Use them to make the stock for soup like this Mushroom soup for instance.

baby mushrooms

This is perhaps one of the most simple mushroom sandwich I have ever made. Except pepper it got no other spices. This recipe is crafted so as to enjoy the full taste and texture of baby portabella mushroom without any interference from other flavours. Glazed with balsamic vinegar these baby portobellos are just rightly flavoured.

So what happens when sweet caramelized onions, cheesy cheddar and spicy shriracha meet with balsamic glazed baby portobellos, the result is super delicious, juicy, meaty filling that you can stuff it inside the slider buns.

mushroom slider sandwich

Caramelizing the onions does takes lots of time. Food lovers are of the opinion that it takes 45 minute to just rightly caramelise the onions, some are ready to show their talent in less than 20 minute also. So if you are not sure how much time it will take for you to get the right caramel color for the onions then prepare it ahead and it will save you lots of time. Mine takes 30 minutes to get the right color I was looking for. But in no case skip the caramelized onions. It is the SOUL of this sandwich.

Cheesy cheddar, yes only that one. No other cheese please, unless you are allergic or have strong reservation against the cheddar cheese. It gives the sandwich a bright yellow color. And that is therapeutic.

mushroom veg burger

Spicy sriracha will add the zing to this fabulous sandwich. But I left it to you. Instead you can try Dijon mustard too. I have used sriracha because I was devoted to sriracha at that time. I was super awed by this wonder sauce.

And finally some greens too. Every burger, sandwiches and slider need some greens. They will make you feel that you are eating something healthy plus the additional crunch it provides. Boston lettuce, rocket and frissee I had at that moment, so I have used that.

Last but not least, serve the sandwich when it still hot or warm. Serve immediately to enjoy the play of flavours, taste and texture of this pure veg delight called mushroom slider sandwich.

Portabella mushroom onion slider sandwich
Prep time
Cook time
Total time
Portabella mushroom slider sandwich with heap of sweet caramelized onions some melted cheddar dash of sriracha and some greens make this a pure veg delight.
Recipe type: Breakfast
Cuisine: American
Serves: 1
  • Baby portabella mushrooms : 1 box (approximately it contains 10-12 mushrooms)
  • Balsamic vinegar (aged) : 2 tbsp or more
  • Red onion (cut into rings) : one very large size (around 2 cups)
  • Sharp cheddar cheese slices : 2
  • Slider buns (or any other buns) : 2
  • Greens : few Boston lettuce, rocket leaves and frissee or any other greens
  • Salt, sugar and pepper to taste
  • Sriracha sauce : a dash of (use as little as possible)
  • Olive oil : 2 tbsp
  1. Wash the baby portabella mushrooms under cold running water and clean them properly.
  2. Pat them dry and thinly slice them.
Caramelizing the onions
  1. Heat some olive oil in the pan.
  2. Cut the onions into rings and add it to the pan. Let them sweat in the pan for around 10 minutes. Keep the heat to the medium .
  3. Sprinkle salt and sugar over it. It will help in the caramelization process.
  4. Keep stirring the onions from time to time. If it is drying out quickly then keep it moist by sprinkling some water over it.
  5. After 20 minutes or so lower the flame and let the onions stick to the bottom a little. But before it burns out, stir them. Continue this process till you get the nice caramelized onions.
  6. So make it ahead and save some time. It will take around 30 minutes.
Making the mushroom melt
  1. In another pan heat some olive oil and once the oil starts simmering add the sliced mushrooms.
  2. Let it sweat for few more minutes.
  3. Once the mushrooms starts changing their color, add the black pepper powder.
  4. Take care not to burn the mushrooms.
  5. Deglaze the pan with balsamic vinegar.
  6. Let the mushroom soak the flavour for another 5 minute.
  7. Check if it needed extra salt or not. Mushrooms will get fully cooked in 10 minute straight.
  8. Meanwhile warm the buns on griddle.
  9. While the mushrooms are still warm, separate it into serving portion and top it with the cheddar slices.
  10. Go for extra sharp cheddar if you can find it.
  11. Let the cheese melts on top of the mushrooms.
  12. Arrange the buns on a serving plate and arrange the greens over it.
  13. Arrange the sandwich in this order - base bun followed by greens, top it with mushroom melt followed by sweet caramelized onions and a dash of Sriracha sauce.
  14. Serve immediately.


mushroom sandwich

Make it enough juicy and with clingy gravy you can serve it on top of open-faced sandwiches too.

What is your favourite way to enjoy the mushroom sandwich ?

Stay tuned for more



  • Reply
    February 19, 2014 at 10:59 pm

    Lovely and mouthwatering to look at mushroom sandwich.

  • Reply
    February 24, 2014 at 11:04 pm

    I am a mushroom fan and what better slider than a mushroom one for me 😀

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