September 22, 2021

Portobello French Dip with Horseradish Aioli

Portobello French Dip with Horseradish Aioli

A classic sandwich that is always sure to hit the spot is the french dip with the combination of savory flavors to be found in between its bread and in the dip itself. But now you can enjoy a meatless alternative that packs enough of a punch with the horseradish aioli it’s paired with thanks to this recipe from Pinch of Yum.

A traditional french dip sandwich utilizes the combination of flavors found in beef, onions, and cheese as well as the “dip” itself. The sandwiches are typically lightly dunked in a brothy type of sauce known as an au jus, and while they’re originally of American origin, they are named after the type of bread they are often made with. This particular recipe is an excellent twist on the old classic thanks to the texture of the portobello mushrooms, deliciously caramelized onions, and spectacular aioli.


Roasted Mushrooms

4 portobello mushroom caps, sliced into thin strips

2-3 tablespoons of olive oil

1-2 teaspoons of Montreal steak seasoning (alternatively salt and pepper)

Caramelized Onions and As Jus

2 tablespoons of butter

1 large onion, thinly sliced

¼ cup of white wine

1 tablespoon of Worcestershire Sauce (omit if vegetarian/vegan)

1 tablespoon soy sauce

2 cups of beef or vegetable broth

Salt, pepper, and a pinch of sugar to taste

Horseradish Aioli

½ cup of mayonnaise

1 teaspoon of horseradish

1 clove of garlic, grated

Pinch of salt

French Dip

4 crusty sourdough rolls or a baguette cut into 4 sections

Provolone cheese slices 


  1. You’ll begin this dish by preheating your oven to 450°F so that you can start roasting your mushrooms. Toss your mushroom slices with oil and seasoning and roast them in the oven for 20-30 minutes.
  2. While the mushrooms are in the oven, melt your butter in a large skillet over medium heat. Once it’s melted, add in your onions, and sauté them until they’ve softened. Then, turn the heat down so that you can caramelize the onions for 20 minutes or so. Stir them occasionally and continue this process just until they’re a deep golden brown.
  3. Now you’ll begin making the au jus. Add your wine to the pan on onions and let it sizzle out. Next, add your Worcestershire and soy sauces, stir the skillet and then add your broth. Simmer the combination until it’s reduced slightly. Pull out the onions with a set of tongs, and set them aside for later. Season the au jus to taste.
  4. Take your bread of choice and prepare them to be toasted. Butter the pieces if you’d like, and then pile your mushrooms onto the bread pieces, cover them with cheese, and return them to the oven on the same roasting pan for 5 minutes or just about enough time to toast the bread and melt the cheese. Be sure to keep a watchful eye during this delicate process so as not to burn anything.
  5. Keep your horseradish ingredients at room temperature and combine the mayonnaise, horseradish, garlic, and salt in a small bowl. Then, set it aside.
  6. Your final step is to top the sandwiches off with caramelized onions, placing a dollop of horseradish aioli onto the sandwiches. Serve alongside the au jus for dipping, and enjoy!


If you are preparing this recipe for a strict vegetarian or vegan, you can easily substitute the Worcestershire sauce for a vegan alternative or soy sauce. Similarly, you can omit the stage in the cooking process that calls for the buttering of the bread prior to toasting.  Additionally, feel free to substitute water for white wine.

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