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A picture of Roasted Mushroom Sandwich with Horseradish Aioli

Roasted Mushroom Sandwich with Horseradish Aioli

  • Author: Lindsay Ostrom
  • Total Time: 40 minutes
  • Yield: this makes enough mushrooms and sauce for 3-4 sandwiches


Layers of roasty mushrooms, havarti, lemony arugula, and an easy homemade horseradish aioli make this mushroom sandwich a WINNER. A saucy, salty, hefty masterpiece!


Units Scale

Roasted Mushrooms

  • 16 ounces sliced mushrooms (portobello or white button mushrooms)
  • 2 tablespoons avocado oil
  • 2 tablespoons Cajun seasoning (if it has salt in it, you may want to add less of it just to make sure the mushrooms don’t get too salty – every brand is different)
  • salt and pepper to taste

Horseradish Aioli

  • 1/2 cup mayo
  • 1 small clove garlic, grated (even half a clove is plenty)
  • 12 teaspoons horseradish sauce, to taste (I use Boar’s Head)
  • 12 teaspoons lemon juice, to taste
  • salt, to taste


  • Big honking chunk of bread that you really love (I like Trader Joe’s caramelized onion focaccia for this)
  • Pesto rosso (optional as a second sauce)
  • Havarti cheese slices
  • Arugula tossed with olive oil and lemon


  1. Roast the mushrooms: Preheat the oven to 450 degrees. Toss the sliced mushrooms with the avocado oil and the seasoning on a sheet pan until well-combined. Roast for 20-25 minutes, until golden brown.
  2. Make the horseradish aioli: Mix all the sauce ingredients in a bowl until well-combined. Taste and season.
  3. Assemble the sandwiches: Toast the bread for the last few minutes on the pan with the mushrooms. Split the bread, spread with pesto rosso, roasty mushrooms, havarti (pop it in the oven again for a minute if you want it to melt), arugula, and the top piece of bread shmeared with the horseradish sauce. OH MY WORD can you even? This is so good.
  • Prep Time: 10 minutes
  • Cook Time: 30 minutes
  • Category: Sandwich
  • Method: No-cook
  • Cuisine: American

Keywords: mushroom recipe, mushroom sandwich, focaccia sandwich, vegetarian sandwich