Portobello French Dip with Horseradish Aioli Recipe

Introduction

This Portobello French Dip with Horseradish Aioli is a hearty, flavorful twist on the classic beef sandwich. Featuring tender roasted mushrooms, caramelized onions, and melty provolone, it’s perfect for a cozy meal that’s both satisfying and vegetarian-friendly.

Ingredients

• 4 portobello mushroom caps, sliced into thin strips
• 2-3 tablespoons olive oil
• 1-2 teaspoons Montreal steak seasoning (or just a sprinkle of salt and pepper)
• 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
• 1/2 cup mayonnaise
• 1 teaspoon horseradish
• 1 clove garlic, grated
• Pinch of salt
• 4 crusty sourdough rolls or a baguette cut into 4 sections
• Provolone cheese slices

Instructions

1. Step 1: Preheat your oven to 450°F (230°C). Toss the sliced portobello mushrooms with olive oil and Montreal steak seasoning (or salt and pepper). Spread them on a baking sheet and roast for 20–30 minutes until tender and slightly browned.
2. Step 2: While the mushrooms roast, melt butter in a large skillet over medium heat. Add the sliced onions and sauté until softened, then reduce heat to low and continue cooking, stirring occasionally, until the onions become deep golden brown and caramelized, about 20 minutes.
3. Step 3: Pour the white wine into the skillet with the onions and let it sizzle until mostly evaporated. Add Worcestershire sauce, soy sauce, and broth. Allow the mixture to simmer until slightly reduced. Use tongs to remove the caramelized onions and set them aside. Season the au jus with salt, pepper, and a pinch of sugar to taste.
4. Step 4: Prepare the horseradish aioli by mixing mayonnaise, horseradish, grated garlic, and a pinch of salt in a small bowl. Adjust the horseradish to taste for desired heat.
5. Step 5: Optionally butter the cut bread. Build the sandwiches by piling roasted mushrooms on the bread, then topping with provolone cheese. Place the sandwiches on the roasting pan in the oven for about 5 minutes to toast the bread and melt the cheese.
6. Step 6: Remove the sandwiches from the oven, top with the caramelized onions, and add a dollop of horseradish aioli to each. Serve immediately alongside the warm au jus for dipping.

Tips & Variations

• For a vegan version, omit the Worcestershire sauce and use vegan mayonnaise and cheese alternatives.
• You can substitute the white wine with extra broth or a splash of apple cider vinegar if preferred.
• Adding fresh thyme or rosemary to the mushrooms before roasting boosts flavor.
• If you enjoy spice, add a pinch of cayenne or a few dashes of hot sauce to the horseradish aioli.

Storage

Store leftover sandwiches wrapped tightly in the refrigerator for up to 2 days. Reheat in a toaster oven or regular oven to keep the bread crisp and the cheese melted. Keep the au jus in a separate container in the fridge for up to 3 days and gently reheat before serving.

How to Serve

Serve this delicious recipe with your favorite sides.

FAQs

Can I use other mushrooms instead of portobello?

Yes, cremini or shiitake mushrooms work well, but portobello’s meaty texture makes it ideal for this sandwich.

Is this sandwich suitable for vegetarians?

Absolutely. Just omit the Worcestershire sauce or use a vegetarian-friendly version and choose vegetable broth.