Portobello “Roast Beef” Sandwiches with Vegan Chipotle Mayo

Mushrooms are definitely my favorite meat substitute. Sliced very thin and sautéed with a little soy sauce and garlic, they’re melt-in-your-mouth soft and bursting with amazing umami flavors. I’ve used that same process in many, many recipes, but today I want to take it a step further to make slices of “roast beef.”

By using portobello mushrooms, we can make large, thin slices that fold perfectly onto a sandwich for the most authentic vegan roast beef sandwich I’ve ever had (actually, it might be the only vegan roast beef sandwich I’ve ever had…). Just to make things a little more ridiculous, we’ll also make a cashew-based mayo with chipotles and smoked paprika, and serve with tomatoes and sprouts or micro greens. I used WHITE BREAD (gasp) Kaiser roll mostly because it made the photos look better, but you can use any healthier sandwich bread or rolls you like (Ezekiel bread would be great).

Makes: 4 sandwiches


  • 6-8 large portobello mushrooms
  • 3 tablespoons soy sauce
  • 1 tablespoon garlic powder
  • 1/2 teaspoon black pepper
  • 1 large beefsteak tomato
  • Microgreens or sprouts
  • Vegan Chipotle Mayo (see below)
  • Sandwich bread or rolls

Step One

The tricky part about this recipe is slicing the mushrooms. You’ll want to start with big portobellos and use a thin, sharp knife to slice layers off the top as thin as you can (less than 1/8″) without having them crumble.

I used about 6 large mushrooms to make 4 sandwiches. And note that it is totally fine to use the little scraps of the mushrooms that you can’t cut into perfect slices. Just slice those bits thinly as well and use them too.

Step Two

With the mushrooms sliced, add them to a large skillet with just a splash of water to start. Let them cook over medium heat for 5 minutes to sweat out most of their moisture and become soft. Drain this liquid out of the pan (we don’t want soggy mushrooms), then add a few drizzles of soy sauce, some garlic powder, and a grind or two of black pepper and allow to cook over medium-low heat for another 10-15 minutes, turning and separating occasionally so that each slice gets fully coated.

Halfway through this process, you may want to add another round of soy, garlic, and pepper. If the pan becomes totally dry, deglaze it with a few tablespoons of water. In the end though, you want the mushrooms to be fairly dry (but not bone dry) so that the flavors can caramelize on their surface. After about 15 minutes when they are very dark and basically melt in your mouth, the mushrooms are done.

Step Three

Slice some tomatoes, grab some sprouts or micro greens, toast whatever bread you’re using (if that’s your thing), and hopefully you’ve made the chipotle mayo too (see below). Then, pile the ingredients onto the sandwich and serve.

Chipotle Mayo

This sandwich just wouldn’t be the same without the creamy chipotle mayo. It’s SO good. If you’re familiar with my style, this mayo should be pretty straightforward: it’s soaked/softened cashews blended with some vinegar, nutritional yeast, and spices to kick it up into a creamy sauce. And this one has dried chipotles as well for an extra kick. Here’s how to make it:

Soak 1/2 cup raw cashews for at least an hour. Drain their soaking water and add to a blender with 1-2 tablespoons nutritional yeast, 1 tablespoon apple cider vinegar, 1+ teaspoon smoked paprika, 1+ teaspoon dried chipotle flakes, 1 teaspoon salt, enough water to blend. Blend thoroughly, then give it a taste and feel free to adjust any spices as needed.

This will make a big batch and you can easily store the leftovers refrigerated in a sealed container for 4+ days.


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  1. Uhhhh….you have definitely captured my attention on this. I am going to try this. Thanks for coming up with this!!!! Major inspiration to create other things with mushrooms. 🙂

    • Oh I was going to mention that – I first tried a mandolin and for whatever reason it did NOT work for me. The slices would start and then get stuck and then break into tiny pieces. I eventually gave up and found a knife to be much easier. I think it’s the size because I know smaller mushrooms do really well in a mandolin.

      • Oh wow – glad I read this comment – I was ready to break out the mandolin. Andrew – you might consider sharing this tip in the main blog – some people with mandolins might not read the comments! This looks amazing – I might add some sesame oil to give a bacon-y flavor. Thanks!

        • I might update it today. I was going to write that in but I’ve been wondering if there’s something wrong with my mandolin, (like it’s gotten dull) because I was surprised at how badly it failed. I’m thinking an extra-sharp mandolin could work and it might be worth a shot if you don’t mind a few extra minutes of cleanup.

          Yes, toasted sesame oil would be awesome too or liquid smoke for a really bacon-y flavor.

          • That’s a good point. If I had some portobellos right now I’d try mine and give a review. The funny thing is, when you described what happened, I could totally imagine mushrooms doing that on a mandolin.

    • Hmm, I would be concerned about freezing it, not sure how well blended cashews would do frozen. It’s possible you could make less but the issue is just having enough volume in the blender to get it blended.

      • I’ve frozen all kinds of cashew dressings and creams before. I just take it out, let it thaw and give it another whiz in my blender and it’s fine. Been doing it a couple years now.

  2. Thank you for the amazing recipe! We have recently (a few weeks ago) gone vegan, using only plant-based ingredients in our diet. This recipe looked good so we tried it. IT WAS A HUGE HIT! It’s on our “regulars” list from now on. We wondered if this would be a meal with protein so just in case, we added black beans seasoned with the same seasoning as the mushrooms. BINGO. Even our meat-loving daughter enjoyed it, saying she didn’t miss the meat at this meal.

    Next time we are going to add caramelized onions, too. YUM!

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