Portobello French Dip with Horseradish Aioli

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It’s hard to describe how much there is to love about these sandwiches, but I’ll try:

Crunchy, buttery, toasted bread is going to meet up with roasted steak-seasoned portobello strips, sweet and golden caramelized onions, a sheet of melted Provolone, and a big thick smear of horseradish aioli…

And then just when you think it can’t even get any better, that whole beautiful crispy, saucy, golden sandwich gets dunked in a richly savory, no-meat-necessary, au jus dipping sauce.

Ingredients for portobello french dip.

It is wonderful, it is meatless, it is the epitome of comfort food.

Dipping portobello french dip into au jus.

Watch how to make this recipe:

French dips are a type of sandwich that normally contain beef, onions, and cheese (also called beef dips) and their trademark is that they get dipped in an au jus (brothy kind of sauce). According to this nice little history of French dips, they are an American invention, but they’re called French due to the type of bread usually used.


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Portobello French Dip with Horseradish Aioli

  • Author: Lindsay
  • Prep Time: 15 minutes
  • Cook Time: 30 minutes
  • Total Time: 45 minutes
  • Yield: 4 mega sandwiches 1x


These Portobello French Dips are about to change your life! Roasty portobello strips, golden caramelized onions, melted Provolone cheese, zippy horseradish aioli, all piled on a warm, crusty roll.



Roasted Mushrooms

  • 4 portobello mushroom caps, sliced into thin strips
  • 23 tablespoons olive oil
  • 12 teaspoons Montreal steak seasoning (or just a sprinkle of salt and pepper)

Caramelized Onions and Au Jus

  • 2 tablespoons butter
  • 1 large onion, thinly sliced
  • 1/4 cup white wine
  • 1 tablespoon Worcestershire (omit for vegetarian / vegan)
  • 1 tablespoon soy sauce 
  • 2 cups beef or vegetable broth
  • salt, pepper, and a pinch of sugar to taste

Horseradish Aioli

  • 1/2 cup mayo
  • 1 teaspoon horseradish
  • 1 clove garlic, grated
  • pinch of salt

French Dip Essentials

  • 4 crusty sourdough rolls, or a baguette cut into 4 sections 
  • Provolone cheese slices



The equipment section above contains affiliate links to products we use and love!

  • Category: Sandwich
  • Method: Oven
  • Cuisine: American

Keywords: portobello mushrooms, french dip, vegetarian sandwich, caramelized onions

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