Portabella Mushroom Sandwich with Caramelized Onions and Jalapeno

Long story short, I saw a meaty version of this sandwich on Serious Eats and immediately started dreaming about the caramelized onion jalapeno combination, and the dream refused to die.  It’s as simple as that.

Hedging my bets that I could make a decent swap using thick strips of portabella mushroom, I decided to give it a try for lunch last weekend.

I loved the end result, and was even more grateful for its success when I unwittingly committed unspeakable acts to an innocent cheesecake later on that evening.

The mushrooms in this sandwich are great, but the leading lady is the sweet and spicy topping.  It all starts with thinly sliced onion, garlic and jalapenos.  I like the heat so I left in the seeds and ribs.

A little while later, you’re ready to build one seriously good sandwich.

And then you’re ready to eat it!

Note: The photos in this post are all from my Android phone, since I left my camera at work.  Not as bad as I was expecting!

Portabella Mushroom Sandwich with Caramelized Onion and Jalapeno
Adapted from Serious Eats


  • 1 Tablespoon vegetable oil
  • 1-2 large portabella mushroom caps
  • Salt and pepper
  • 1 Tablespoon unsalted butter
  • 1 medium yellow onion, thinly sliced
  • 1 fresh jalapeño pepper, thinly sliced (see Notes)
  • 1 garlic clove, thinly sliced
  • 1 Tablespoon Worcestershire sauce
  • 1 teaspoon sugar
  • 1/4 cup milk
  • 2 sturdy rolls, halved lengthwise
  • 2 cups loosely packed salad greens


  1. Heat oil in large skillet over medium-high heat.  Brush mushroom slices with olive oil, then generously sprinkle with coarse salt and pepper.  Cook mushrooms until golden, then transfer to a plate and tent with foil.
  2. Melt butter in now empty skillet.  Add onions, jalapenos, garlic, Worcestershire sauce, and sugar and season with salt and pepper.  Cook, covered and stirring occasionally, until vegetables are soft and deep golden, 15 to 20 minutes.
  3. Stir in milk and any accumulated mushroom juices and cook just to heat through, about 2 minutes.  Adjust seasoning.
  4. To assemble, top one side of each roll with optional greens and arrange mushrooms on top.  Top with onions and jalapeno.  Serve warm.

Serves 2.

Print Version

7 thoughts on “Portabella Mushroom Sandwich with Caramelized Onions and Jalapeno

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