Roasted Portobello Mushroom Sandwich

Enjoy this gourmet Roasted Portobello Mushroom Sandwich Recipe with herbed, breaded portobellos topped with grilled onions and a delicious tangy brown sauce. Mushroom Sandwich recipes are best with this portobello marinade! Be sure and make this Portobello Sandwich today!

A crispy roasted portobello sandwich with green sprigs on top sits on a white plate topped with red napkins.

I love a good sandwich. Adding crispy, marinated mushroom pieces topped with a tangy hoisin sauce just makes my day!

A veggie sandwich on a white plate topped with red napkins.

Why Mushrooms?

There’s no denying, mushrooms are good for you! But there’s another reason to include them in your vegan kitchen. Mushrooms also have a meaty texture that many people go to when they first take on a vegetarian or vegan diet.

If you’ve not worked with mushrooms before, these step-by-step instructions will help you take on this sandwich with ease!

How to Make Roasted Portobello Mushroom Sandwich

Here are the steps to make this roasted portobella sandwich. Start with 5 large portobellos. Wash and dry them and remove stems. Then cut them into 6 pieces each.

Looking down on a portobello mushroom chopped into 6 pieces.

Place those mushroom pieces in a large bowl. Then make the portobello marinade made of mirin, sherry, and olive oil. Toss, mushrooms in the marinade. It helps to use your hands to coat and toss the mushrooms.

Once the mushrooms are adequately covered, set aside and let marinate for about 20-30 minutes.

Portobello mushroom pieces marinating in a metal bowl.

Preheat your oven’s broiler to high.

In a saucepan over medium heat, add some oil and sliced onions. Cook the onions until tender and then add a little bit of coconut sugar and cook a few more minutes until the onions are caramezlied.

Make a Spicy Tangy Brown sauce by combining hoisin, tamari, vegan Worcestershire, dried ginger powder, and water in a bowl.

Three bowls contain a hoisin sauce, caramelized onions, and sprigs of cilantro.

Add bread crumbs to the bowl of marinated portobello mushrooms and shake to coat. Line a baking sheet with foil and lightly spray with cooking spray.

Place the breaded mushrooms on the pan and then place it under the broiler for around 10 minutes. Remove from the oven and use tongs to turn the mushroom pieces. Return to the oven and bake for another 10 minutes.

Breaded portobello pieces on a baking sheet covered with foil.

To assemble each portobello sandwich, spread some sauce on the bottom buns, then add several crispy Portobello cubes. Top that with caramelized onions, drizzle with more sauce, and top with cilantro sprigs.

A hoagie bun holds mushroom pieces, caramelized onions, and greens.

And now for the best part of all – dig in!

Side Dishes

What can you serve with this roasted portobello sandwich? How about some air fryer french fries! Those are a go-to favorite around here. I think a batch of my favorite Brussels Sprouts Slaw would be great too! Or how about a big batch of vegan potato salad to round this tasty dish out!

Looking down on a veggie sandwich topped with mushroom pieces, and greens.

Veggie Num Num's vegan version of a Crispy Drunken Chicken Sandwich

Crispy Drunken Portobello Sandwich

Enjoy this gourmet roasted portobello sandwich with herbed, breaded portobellos topped with grilled onions and a delicious tangy brown sauce.
5 from 2 votes
Course: Main Course
Cuisine: American
Prep Time: 15 minutes
Cook Time: 25 minutes
Resting Time: 10 minutes
Total Time: 40 minutes
Servings: 4
Calories: 174kcal


  • 5 large Portobello mushrooms washed and patted dry
  • 2 tablespoon mirin (see note)
  • 1 teaspoon sherry
  • 2 tablespoons olive oil, divided
  • 1 large yellow onion, peeled and sliced thin
  • 1 teaspoon coconut sugar
  • ¼ cup panko crumbs
  • 4 sourdough sandwich rolls
  • ¼ cup fresh cilantro leaves

Tangy brown sauce:


  • Remove stems from Portobellos; slice each cap into 6 cubes. Place those cubes into a large bowl.
  • In a small bowl, combine the mirin, sherry, and 1 tablespoon olive oil; drizzle over the mushrooms. Using your hands, gently coat and toss the mushrooms with the mirin mixture. Set aside and let marinate for about 20-30 minutes.
  • While the portobellos cubes are marinating, preheat the broiler to high. 
  • Heat the olive oil in a large sauté pan and add onion slices. Cook onions for 5 – 7 minutes and add the sugar and stir to combine. Cook another 5 minutes until the onions brown and caramelize. 
  • To make the tangy hoisin sauce, whisk together the hoisin, tamari, Worcestershire, dried ginger, and water.
  • Add the bread crumbs to the bowl of mushrooms and coat thoroughly. Line a baking sheet with foil and lightly spray with cooking spray. Add the marinated mushrooms and place directly under the broiler for 10 minutes. Use tongs to turn the mushrooms and pour any extra sauce over them. Then return the pan to the oven and cook for another 10 minutes.
  • To assemble the sandwiches, spread some hoisin sauce on the bottom bun, then top with several crispy Portobello pieces. Top with grilled onions, more sauce, and some fresh cilantro leaves. Top with top bun piece.

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If you don’t have access to mirin, you can sub with a sweet white wine.
Note: Nutrition information does not include sourdough buns.
Calories: 174kcal | Carbohydrates: 22g | Protein: 4g | Fat: 8g | Saturated Fat: 1g | Sodium: 719mg | Potassium: 466mg | Fiber: 2g | Sugar: 11g | Vitamin A: 70IU | Vitamin C: 3.1mg | Calcium: 24mg | Iron: 1mg

The nutrition information shown is an estimate provided by an online nutrition calculator and should not be considered a substitute for a professional nutritionist’s advice.


14 Responses to Roasted Portobello Mushroom Sandwich

  1. Avatar thumbnail image for MarlyJason Reply

    Yum! That looks sooo good.

  2. Avatar thumbnail image for MarlyCookin' Canuck Reply

    What a great idea! I’m looking forward to checking out all of the vegan sandwich ideas.

5 from 2 votes

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