This grilled portobello mushroom burger topped with generous pile of sweet caramelised onions has fantastic meaty texture and is rich in umami flavours. Vegan hit!
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Who said that veggie burgers have to be boring? Believe me when I say that my Portobello Mushroom Burger recipe is far from it! It has even got seal of approval from beef burger loving carnivores!
Meaty texture of portobello mushroom caps makes them perfect meat patty substitution and delicious and rich marinade adds all the flavour you need. Boring? Definitely not!
Instead be prepared for super juicy and also slightly messy (especially if you like to pile your burger up high) flavour sensation!
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Caramelised Onions & Harissa Mayo
As if beautifully marinated and grilled to perfection portobello mushroom wasn't enough on its own, I decided to go a step further and add couple of most delicious accompaniments that make this mushroom burger the bee's knees!
Harissa Mayo
Made with two simple ingredients: vegan mayonnaise* and harissa paste* it makes for perfect condiment with gently smoky flavour and a bit of chilli heat.
Personally, I love to spread it in a thick layer onto the bottom half of my burger bun before piling up the remaining components of my portobello mushroom burger. Simply lush!
You can of course use any other condiment for your burger, I won't tell.
Caramelised Onions
As I'm not a fan of sliced raw onions in my burger, these soft, sweet and slightly tangy caramelised onions were a no-brainer really.
I would urge you not to skip them as they are so worth that tiny bit of extra effort!
Even more serving suggestions
Beside my two most delicious additions mentioned above, the world really is your oyster here, it is a burger after all.
Further toppings could include and are by no means limited to
- sliced tomatoes
- avocado slices
- sweet & sour gherkins
- your favourite vegan cheese
- red onion slices
- your favourite lettuce or salad leaves
- fresh herbs
- roasted peppers
As for the bready bit simply use your favourite burger buns or if you're a keen baker I've got a fantastic burger bun recipe coming your way very soon so watch this space.
In the meantime, you could give my Easy Yogurt Bread Rolls a go or if you fancy something a little bit different my Easy Flatbreads would be fantastic for having your grilled portobellos in too.
I would also recommend my delicious Baked Polenta Chips, Corn Ribs and Vegan Potato Salad on the side (just saying).
What if you don't have a grill pan?
It's not a problem at all as you can fry your mushroom caps in a frying pan instead. The only difference will be the lack of characteristic grill marks.
You outdoor bbq would be another obvious choice.
Pro Tips
This recipe is really simple but there are few things you might want to bare in mind to ensure your burger is absolutely perfect.
- Make sure you don't skimp on marinade! Be very generous when it comes to brushing it all over your mushrooms as they marinade as well as during grilling. Make sure you get it into all the nooks and crannies for maximum flavour.
- Don't be afraid of your spatula* and do press down on your mushrooms like you mean it (but gently). On the contrary to meat patties, this will not dry them out at all but will add even more flavour due to caramelisation and ensure perfect flatness for the easy assembly of your burger.
- My last tip would be to use two portobello mushroom caps per burger for a double decker burger experience! Call me greedy but sometimes only that will do.
How to make Portobello Mushroom Burger
- Start with preparing your portobello mushrooms by giving them a wipe with a damp paper/kitchen towel and removing the stems.
- In a shallow dish that will fit all four mushroom caps mix together ingredients for the marinade.
- Place the mushrooms in the dish (tops of the caps down), brush the other side with generous amount of marinade and let them sit and soak up the flavours for 15 minutes.
- After approximately 15 minutes flip your portobello mushroom caps top side up and brush with some more marinade. Let them sit in the dish for another 15 minutes if you have time or give them 5 minutes and get grilling.
- Drizzle some rapeseed oil onto the grill pan* and make sure it is distributed evenly (I like to brush it on with a silicone brush*).
- Put your pan onto a medium heat and place your portobello mushroom caps bottom side down in the pan.
- Grill for 5-7 minutes pressing down (gently) with a spatula from time to time to get a little bit of caramelisation going as well as to get that flat patty shape.
- Flip your mushrooms over and repeat the process brushing some extra marinade on your mushroom caps as you go.
TIP: For criss-cross grill marks make sure to rotate your mushroom caps on the grill pan when top side down.
How to make Caramelised Onions for your burger
- Thinly slice some white onions and fry them in a pan with a little bit of rapeseed oil nice and slow until softened, sweet & translucent. It will take anything from 30-45 minutes.
- Once your onions are nice and soft add tablespoon of balsamic vinegar, ½-1 tablespoon of demerara sugar, stir and continue frying for another 5 minus or so.
- Use as a topping for your portobello mushroom burger!
Have you tried my Portobello Mushroom Burger?
Please consider giving it ⭐️⭐️⭐️⭐️⭐️ rating in recipe card below and share your views or tips in the comments.
More delicious recipe you might want to try
Easy Chickpea & Carrot Falafel Burger
Vegetarian Sausage Rolls
Homemade Fresh Tomato Salsa (Pico De Gallo)
Easy Yogurt Bread Rolls
Easy Flatbread (No Yeast)
📋 Recipe
Portobello Mushroom Burger with Caramelised Onions (Vegan)
Equipment
Ingredients
Burgers
- 4 portobello mushrooms cleaned and stems removed
- 1 tablespoon rapeseed oil to grease the grill pan with
Marinade
- 2 tablespoon balsamic vinegar
- 2 tablespoon Extra Virgin Olive Oil
- 1 tablespoon soy sauce or tamari
- 1 teaspoon dried oregano
- ½ teaspoon garlic powder
- ½ teaspoon onion powder
Caramelised Onions
- 3 medium onions approx. 250-290g, peeled and thinly sliced
- 1 tablespoon rapeseed oil
- 1 tablespoon balsamic vinegar
- ½-1 tablespoon demerara sugar
Harissa Mayo
- 8 tablespoon vegan mayo
- 2 teaspoon harissa paste
- burger rolls, sliced tomatoes, lettuce etc. to serve
Instructions
Portobello Mushroom Burgers
- Start with preparing your portobello mushrooms by giving them a wipe with a damp paper/kitchen towel and removing the stems.
- In a shallow dish that will fit all four mushroom caps mix together ingredients for the marinade.
- Place the mushrooms in the dish (top of the caps down), brush the other side with generous amount of marinade and let them sit and soak up the flavours for 15 minutes.
- After approximately 15 minutes flip your portobello mushroom caps top side up and brush with some more marinade. Let them sit in the dish for another 15 minutes if you have time or give them 5 minutes and get grilling.
- Drizzle some rapeseed oil onto the grill pan and make sure it is distributed evenly (I like to brush it on).
- Put your pan onto a medium heat and place your portobello mushroom caps bottom side down in the pan.
- Grill for 5-7 minutes pressing down gently with a spatula from time to time to get a little bit of caramelisation going as well as to get that flat patty shape.
- Flip your mushrooms over and repeat the process brushing some extra marinade on your mushroom caps as you go.
Caramelised Onions
- Thinly slice some white onions and fry them in a pan with a little bit of rapeseed oil nice and slow until softened, sweet & translucent. It will take anything between 30-45 minutes.
- Once your onions are nice and soft add tablespoon of balsamic vinegar and ½-1 tablespoon of demerara sugar. Stir and continue frying for another 5 minus or so.
- Use as a topping for your portobello mushroom burger!
Harissa Mayo
- Mix harissa paste with vegan mayo in a small bowl until combined. Serve with your burger.
Burger Assembly
- Serve grilled portobello mushroom burgers in burger buns or flatbreads with your choice of additions (sliced tomatoes, lettuce, gherkins, avocado, harissa mayo etc.) and topped with caramelised onions.
Video
Notes
- Nutritional information is approximate and per one portobello mushroom burger with a portion of caramelised onions. Burger buns, sauces etc. haven't been included in the calculation.
- In the absence of grill pan, use regular frying pan or even outdoor BBQ.
- Don't skimp on marinade! Make sure you use every single drop for brushing over your mushrooms when marinating and using any leftovers to brush over when grilling too.
- Don't be afraid of your spatula and press down (gently) on your mushrooms from time to time as they cook to ensure some caramelisation which equals even more flavour and to get that flat patty shape.
- For criss-cross grill marks make sure to rotate your mushroom caps on the grill pan when top side down.
- Go to town and use two portobello mushroom caps per burger instead of one for delicious double decker experience!
Please leave a comment & rating if you've made my recipe! Feel free to ask questions too, I reply to all!