A towering mushroom Reuben that channels the flavours of the deli classic

Becky Krystal

THE WASHINGTON POST – I have long enjoyed everything about the Reuben sandwich – except the corned beef. To me, it’s always been secondary to the griddled rye bread, zippy Russian dressing, gooey Swiss cheese and crunchy sauerkraut.

I often gravitated toward what many delis call the Rachel, not the infamous Jennifer Aniston haircut, but rather a Reuben made with turkey. These days, I find myself eating much less meat and poultry. I wanted to see whether I could come up with a vegetarian version that was just as satisfying.

Of course, the temptation is to just leave out the protein entirely. That felt a bit defeatist, and then really all I’d have was a grilled cheese with a bunch of condiments (not that there’s anything wrong with that). I wanted something more substantial, that would replicate the stateliness and height of the original. I’ve had a few restaurant versions made with tempeh and liked them, but the fermented soybean product didn’t quite fit the profile for me for this recipe, so I turned to that classic, “meaty” vegetarian staple, the portobello mushroom.

Initial tests were promising, if not perfect. Roasting thinly sliced portobello caps at a high heat cooked off so much moisture I practically had mushroom jerky. Tasty, but the sandwich felt more like a mushroom melt. Next, I tried whole caps. They didn’t cook down enough, leaving me with mushrooms that were too thick, squeaky and stringy for my taste. For help, I turned to Washington chef Rob Rubba, whose restaurant Oyster Oyster places an emphasis on locally foraged mushrooms. I was already ambivalent about having to use both the oven and stove top to make the sandwich, and he suggested I consider pressing mushrooms in the skillet. My next test involved slicing the portobello caps in half through the equator, arranging them in layers in a non-stick pan and weighing them down with a cast-iron skillet. Bingo. The mushrooms gave up most, but not all, of their liquid, leaving me with stackable slices with just enough bite and juiciness to almost replicate a pile of deli cuts.

Rubba also mentioned that sometimes he rubs the mushrooms with a miso-mustard mix to get a crust that in this case would offer some of the same textural contrast as corned beef. Again, he was spot on.

I assembled a spice and Dijon mustard paste that incorporated a few of the ingredients you might find in the pickling brine for the beef – all spice, mustard, red pepper flakes, salt, black pepper and coriander. Spread onto the mushroom slices and briefly browned in the skillet, it added the right amount of punch and crunch. The rest was straightforward.

Sliced Swiss, check. Rye bread, check (you can use seeded, seedless or marble). Russian dressing, check. I’m offering a modified version of the dressing from The Washington Post archives, but feel free to use store-bought. All that was left was to griddle the sandwich – a mushreuben, as my colleague Kari Sonde and others have called it – to golden brown perfection and dig in. Even without the meat, it will meet with your approval.



This take on the deli classic replaces the corned beef with slices of portobello mushrooms for a satisfying sandwich featuring zesty Russian dressing, melty Swiss cheese and tangy sauerkraut. Pressing the sliced mushrooms in a skillet eliminates excess moisture while retaining a juicy bite, and a mustard-and-spice paste incorporates some of the flavours you would otherwise find in the typical corned beef. The number of slices you end up with will depend on the size of the portobellos. Expect from eight to 16 slices total.

If you don’t feel like making the Russian dressing from scratch, substitute your favourite store-bought variety.

Recipe notes: The sum total of these ingredients makes for a high-sodium meal, though steps such as using less dressing, finding a low-sodium or homemade bread and reducing the salt in the spice rub can help bring the numbers down, if desired.

Leftover dressing can be stored in an airtight container for up to three days. Extra mushrooms can also be refrigerated for a few days for additional sandwiches, though you may want to warm them slightly or allow to come to room temperature before using.



Quarter cup mayonnaise

Quarter cup ketchup

One-and-a-half teaspoons prepared (white) horseradish or peeled, grated horseradish root, patted dry

Half teaspoon hot paprika (may substitute sweet paprika and a pinch of cayenne pepper)

One tablespoon chopped pickles

One clove garlic, minced


Two tablespoons Dijon mustard

Two teaspoons ground coriander

One teaspoon brown mustard seeds

Half teaspoon kosher salt

Quarter teaspoon red pepper flakes

Pinch ground all spice

Freshly ground black pepper

Vegetable oil

One pound portobello mushrooms, sliced in half horizontally


Four slices rye bread (seeded, seedless or marble)

Four slices Swiss cheese

Two-third cup sauerkraut, drained

One tablespoon unsalted butter (may substitute salted butter)


Make the dressing

In a medium bowl, using an immersion blender, process the mayonnaise, ketchup, horseradish, paprika, pickles and garlic, pulsing until well combined. (You can also use a food processor, but consider doubling the batch for easier processing.) The yield is about half cup; you’ll have extra for more sandwiches or other uses. Transfer to an airtight container and refrigerate until needed.

Make the mushrooms

In a small bowl, stir together the mustard, coriander, mustard seeds, salt, red pepper flakes, allspice and a few grinds of black pepper until thoroughly combined.

Coat the bottom of a 12-inch nonstick skillet with a thin layer of oil and set over medium heat for several minutes, or until you feel a decent blast of heat when holding your hand an inch or so above the skillet. Arrange the mushrooms in the skillet in two layers. Wrap the bottom of a cast-iron skillet or a plate (weighted with heavy cans) in foil and place on top of the mushrooms; the goal is to press the liquid out of the mushrooms. Cook, undisturbed, for six minutes. Remove the skillet or plate, flip the mushrooms over, arranging them so the thickest slices are toward the middle, or the hottest part of the pan. Return the skillet or plate on top of the mushrooms and cook until the mushrooms have significantly reduced in size and almost all the liquid has evaporated, another five to six minutes. If there’s still liquid in the skillet, uncover the mushrooms, briefly increase the heat to medium-high and cook until the water is mostly gone.

Transfer the mushrooms to a platter and spread an even, thin layer of the mustard mixture on one side of each mushroom slice. (On the slices from the top halves of the mushrooms, the mixture adheres best to the exterior rather than the flesh.)

Wipe out the skillet, add another thin coating of oil and return to medium heat (no need to preheat more than one minute or so, as it will still be quite hot). Place the mushrooms in a single layer, coated side down, and cook until browned and crisp in spots, two to three minutes, working in batches. A little of the coating may come off; that’s okay – just pile it on when assembling the sandwiches. Wipe the skillet clean.

Make the sandwiches

Spread about one tablespoon of the dressing on each of the four slices of bread. On two of them, build the sandwiches, evenly dividing the cheese, mushrooms and sauerkraut, followed by the other two slices of bread. In the skillet over medium heat, melt the butter until bubbling slightly. Griddle the sandwiches on both sides (do one at a time if you’re tight on space) until golden brown and crisp, two to three minutes per side. Cut in half and serve.