One of the easiest and tastiest vegan burgers you can make is a Portobello Mushroom Burger. Why is it different from any other veggie burger? Well, portobello mushrooms are marinated in a fajitas spice mix and layered among guacamole, salsa, nacho cheese sauce, and spicy fajitas veggies. This portobello burger is piquant and scrumptious at the same time.
This mushroom burger recipe was inspired by our Vegan Portobello Mushroom Fajitas. It is rich, colorful, and full of flavors. We love Tex-Mex food. Can’t you tell? Our favorite large batch meal prep recipe is Vegan Bean Chili with Millet. We also make all to often this Vegan Nut-free Nacho Cheese Sauce. It is just so delicious. That is why it got a prominent place in this burger recipe.
What is a portobello mushroom burger?
If you’ve never eaten it before, then you are in for a treat. In this burger recipe, you marinade and grill large portobello mushroom caps in whole and use them instead of regular burger patties. Obviously, it is something different from a beef burger. I would say it is closer to grilled chicken in terms of texture. You can add the grilled mushroom caps as the meaty layer to any burger recipe and enjoy it like that. May it be with a hamburger bun full of shredded lettuce, sliced tomato, and red onion rings or…
So why should you try this Spicy Fajitas Vegan Burger recipe? I can list several reasons.
This grilled portobello mushroom burger…
- is piquant and creamy at the same time.
- is full of rich and colorful ingredients.
- has a charred flavor and a meaty texture.
- is healthier than beef burgers.
- is easy to make and incredibly tasty.
In one word, it is EPIC. Need I say more? Now, let’s see how to make one!
The first step is to marinate the mushroom caps
How do you marinate them? Take a small-sized bowl. Add olive oil, salt, black pepper, minced garlic cloves, freshly squeezed lime juice, and your favorite spice mix. In this Tex-Mex inspired recipe, we added fajitas spice mix and some extra sweet smoked paprika, just because we like it. Stir until combined. This is how our marinade looks, see below.
If you don’t have a fajitas spice mix in your pantry, don’t worry you can easily make your own. To make homemade fajitas spice mix, use the below spices. (The exact amounts will be in the recipe card.)
- hot chili powder,
- sweet smoked paprika,
- garlic powder, and
Now, peel the portobello aka portobella mushrooms. Take out the stems. We use a glass bowl, which is also our meal prep bowl actually. Place the mushroom caps and pour the marinade on top of them. Use a silicone brush to spread the marinade. Toss and turn a couple of times, to make sure they are covered everywhere. Repeat this step after an hour (in case of short marinate) or in the morning (in case of overnight marinate) to make sure mushrooms are not getting dry. It will look as it is in the below picture.
Top tips to marinate mushrooms
- How long? – Mushrooms have a spongy texture. Therefore, the longer they soak in the marinade, the more intense the flavor will be as they absorb more. We recommend overnight soaking, but 2 hours should be the bare minimum to get them seasoned.
- How much? – You don’t need to make a lot of marinades as you don’t need to immerse the mushroom caps in it. We do flip them or brush them a couple of times.
- Hot or sweet? – In case you prepare the burger for kids or for people who don’t like spicy food, you can skip the hot chili powder and add more sweet smoked paprika powder.
- Powder vs fresh ingredients? -We like using fresh ingredients if we have them, but you can use onion powder or garlic powder instead.
How to grill portobello mushrooms?
You can prepare portobello mushrooms for your burger 3 ways: bake them, grill them or pan fry them.
How to fry them on a stove?
The easiest way is if you have a grill pan and you cook them on a stovetop. First, heat the grill pan to medium. Once sizzling hot, place the marinated mushroom caps on it. Cook both sides for approx. 5 minutes. You can push the mushrooms down for a few seconds each side with a spatula to allow the greater surface of the mushrooms to be grilled. Brush each side with the leftover marinade once. Cover the grill pan to allow hot air to circulate through the pan (just as it would in a real gas grill). That is all! You can see how they look when ready in the below picture. Now, you are ready to assemble your vegan burger.
How to bake them in the oven?
You can use a glass oven-safe dish or a grill pan (provided that the handle is not made of plastic). Pre-heat the oven for 400 Fahrenheit (200 degrees Celcius) and grill them under the broiler for 10 minutes, turning them half time.
How to grill them on a gas grill without burning?
Our little trick to grilling mushroom is to use aluminum foil drip pans. Similar to the oven grilling, pre-heat your gas grill for 400 Fahrenheit (200 degrees Celcius) and grill the marinated portobello mushroom caps for 10 minutes, turning them half time.
Let’s build your Fajitas Burger
The best part of the whole recipe is building your yummy vegetarian burger. I know that the more layers you add, the harder it is to eat. However, I really-really recommend all these layers for you to try. They are absolutely amazing and delicious together!
- I started off with a toasted bun.
- First up is a generous spread of Salsa sauce.
- Then, I added green leaf lettuce because the ruffles look so pretty.
- Next up, some spicy, nut-free, and veggie-packed Nacho Cheese Sauce.
- Then, we quickly made 2 servings of our Fajitas Veggies (roasted bell peppers and red onions).
- Now, the star of the burger the grilled portobello mushroom caps.
- Finish it off, we some homemade Guacamole.
What else can you add?
To take it even further, we love to add another layer of grilled mushroom caps below the cheese sauce! So tasty and filling! And look how beautiful the layers are below! You can also add tomato slices instead or on top of the salsa sauce. Or avocado slices instead of guacamole.
This Vegan Portobello Mushroom Burger recipe is vegan, so meat-free, dairy-free, and egg-free. It is also suitable for vegetarian, nut-free, and gluten-free diets. It is not suitable for an oil-free plant-based diet, as you cannot substitute olive oil in the marinade and get the same result as on the pictures.
More grilling recipes
- Grilled Vegetable Kabobs
- Vegan Beetroot Burger
- Chinese BBQ Tofu Burger
- The Meatiest Vegan Burger (in Big Mac Style)
- Grilled Buffalo Tofu Skewers
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Epic Fajitas Portobello Mushroom Burger
Portobello Mushroom Marinade
Homemade Fajitas Spice Mix
Make the fajitas marinade
- Take a small-sized bowl. Add olive oil, salt, black pepper, fresh garlic cloves, freshly squeezed lime juice, and your favorite spice mix. Stir until combined.
Soak mushrooms in marinade (min. 2 hours, but overnight is preferred)
- Peel the portobello mushrooms. Take out the stems.
- Place the mushroom caps in a shallow bowl and pour the marinade on top of them.
- Toss and turn a couple of times, to make sure they are covered everywhere.
- Repeat this step after an hour (in case of short marinate) or in the morning (in case of overnight marinate) to make sure mushrooms are not getting dry.
Pan-frying portobello mushrooms on a stove
- Heat the grill pan to medium. Once sizzling hot, place the marinated mushroom caps on it.
- Cook both sides for approx. 5 minutes. You can push the mushrooms down for a few seconds each side with a grill spatula to allow the greater surface of the mushrooms to be grilled.
- Brush each side with the leftover marinade once.
- Cover the grill pan to allow hot air to circulate through the pan (just as it would in a real gas grill).
Assemble your Meatless Portobello Mushroom Burger
- Take the bottom part of a hamburger bun (if you toasted it a bit - even better)
- Spoon some salsa sauce on the first part of the burger.
- Add a couple of green leaf lettuce leaves.
- Spoon some Nacho Cheese Sauce (We have a Nut-free, Vegan Nacho Cheese Sauce recipe).
- Add fajitas bell pepper and onion slices. (We have a detailed guide on how to make Fajitas Veggies the EASIEST WAY).
- Add the grilled portobello mushroom caps.
- Finish it off with some guacamole.