Portobello French Dip with Horseradish Aioli Recipe
This Portobello French Dip with Horseradish Aioli is a savory vegetarian twist on the classic French dip sandwich. Featuring roasted portobello mushrooms seasoned to perfection, caramelized onions, melted provolone cheese, and a tangy horseradish aioli, this sandwich is served on crusty sourdough rolls and accompanied by a flavorful au jus for dipping. Perfect for a hearty meal that’s full of rich, comforting flavors without the meat.
- Prep Time: 15 minutes
- Cook Time: 50 minutes
- Total Time: 1 hour 5 minutes
- Yield: 4 sandwiches 1x
- Category: Sandwich
- Method: Roasting
- Cuisine: American
- Diet: Vegetarian
Ingredients
Scale
Roasted Mushrooms
- 4 portobello mushroom caps, sliced into thin strips
- 2–3 tablespoons olive oil
- 1–2 teaspoons Montreal steak seasoning (or salt and pepper to taste)
Caramelized Onions and Au Jus
- 2 tablespoons butter
- 1 large onion, thinly sliced
- 1/4 cup white wine
- 1 tablespoon Worcestershire sauce (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 mayonnaise
- 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 (about 4 slices, one per sandwich)
Instructions
- Roast the Mushrooms: Preheat your oven to 450 degrees Fahrenheit. Toss the thinly sliced portobello mushrooms with olive oil and Montreal steak seasoning (or salt and pepper). Spread them out on a roasting pan and roast for 20 to 30 minutes until tender and slightly caramelized.
- Caramelize the Onions: While the mushrooms are roasting, melt butter in a large skillet over medium heat. Add the thinly sliced onions and sauté until softened. Lower the heat and continue cooking the onions for around 20 minutes, stirring occasionally, until they turn deep golden brown and caramelized.
- Make the Au Jus: Pour the white wine into the skillet with the caramelized onions to deglaze the pan. Let the wine sizzle and reduce slightly. Add Worcestershire sauce and soy sauce, then pour in the broth. Allow the mixture to simmer gently until it reduces slightly to intensify the flavors. Remove the onions with tongs and set aside. Season the au jus with salt, pepper, and a pinch of sugar to taste.
- Toast the French Dips: Optionally butter the inside of the sourdough rolls or baguette sections. Layer the roasted mushrooms onto the bread, then top each with a slice of provolone cheese. Place the sandwiches back on the roasting pan in the oven for about 5 minutes—just enough to toast the bread and melt the cheese.
- Assemble and Serve: Top each sandwich with the caramelized onions. Add a dollop of the prepared horseradish aioli on top. Serve the sandwiches hot with a small bowl of the savory au jus on the side for dipping and enjoy the rich, comforting flavors!
Notes
- To make this recipe vegan, omit the Worcestershire sauce and replace mayonnaise with a vegan mayo alternative.
- If you prefer, you can substitute beef broth with vegetable broth to keep it fully vegetarian.
- The horseradish aioli adds a spicy tang; adjust the horseradish quantity based on your heat preference.
- Roasting mushrooms at a high temperature enhances their umami flavor and texture.
- Caramelizing onions requires patience but adds important sweetness and depth to the sandwich.
- Use crusty bread like sourdough or baguette for the best texture and to hold up to dipping in the au jus.
Keywords: Portobello French Dip, French Dip Sandwich, Vegetarian French Dip, Roasted Mushrooms Sandwich, Horseradish Aioli, Caramelized Onions, Au Jus, Comfort Food
