This pastrami, caramelized onion, and Gruyère sandwich combines peppery meat, sweet onions, and the subtle yet essential tang of cheese in this easy, satisfying meal.
Onion rye, sliced sourdough, or challah would all be great breads for this sandwich. At Macrina, we often feature it on our pretzel knot roll, a fairly dense roll made with the addition of a little rye flour, then topped with coarse salt, poppy seeds, and sesame seeds. The combination of these flavors with the American favorite delicacy of thinly sliced peppery pastrami plus sweet caramelized onions and nutty Gruyère cheese is terrific.–Leslie Mackie
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*What’s the difference between pastrami and corned beef?
There are a couple differences. Corned beef is made from brisket, which comes from the lower chest of the cow; pastrami is typically made either from a lean, wide, firm shoulder cut, or a smaller and juicier section right below the ribs, although you may occasionally see pastrami made from brisket. The biggest difference is the spices used. Corned beef is, well, naked. Aside from the flavor of the brine, it doesn’t have much else added. Pastrami, on the other hand, is coated with black pepper, coriander, mustard seeds, fennel seeds, and sometimes fresh garlic.
For the caramelized onions
- 4 tablespoons (2 oz) unsalted butter
- 2 medium yellow or Walla Walla onions cut into 1/8-inch (3-mm) slices
- 1 teaspoon chopped thyme leaves
- 1/4 teaspoon crushed red pepper flakes (optional)
- Kosher salt to taste
For the mustard aioli
- 1 large egg yolk
- 1/2 teaspoon finely chopped garlic
- 1 1/2 teaspoons fresh lemon juice
- 1 plus 1 teaspoon Dijon-style mustard
- 1/2 cup canola oil
- Kosher salt to taste
For the sandwiches
- 4 pretzel rolls or other sandwich rolls or sturdy bread
- 2 tablespoons (1 oz) unsalted butter at room temperature
- 10 to 12 thin slices (14 oz) good-quality pepper-crusted pastrami*
- 4 ounces Gruyère cheese thinly sliced
Make the caramelized onions
- In a large nonstick skillet over medium-low heat, melt the butter. Add the onions and toss to coat. Cook until the onions have softened, about 5 minutes.
- Add the thyme and red pepper flakes, if using, to the onions and continue to cook, stirring frequently so they brown evenly, for up to 60 minutes or more. (If the heat is too hot, the onions will burn, so slow it down and take some time to enjoy the process.) Season with salt to taste and dump the onions in a large bowl.
Make the mustard aioli
- Whisk the egg yolk, garlic, lemon juice, and mustard in a medium bowl to thoroughly combine. Start adding the canola oil, just a few drops at a time, whisking constantly, until the mixture begins to emulsify. As it thickens, continue adding the oil in a slow stream, making sure each addition is thoroughly blended before adding more. Season to taste with salt. Cover the aioli and refrigerate until needed.
Assemble the sandwiches
- Position a rack in the center of the oven and preheat to 350°F (176°C). Line a rimmed baking sheet with parchment paper.
- Cut each roll in half horizontally. Butter the cut sides of the rolls and place them, cut side down, on the baking sheet. Toast the rolls in the oven for 3 to 5 minutes, until the butter is melted and the rolls are warm.
- Flip each roll over so that the cut side is up. Spread each side with some mustard aioli. Place equal amounts pastrami on the bottom half of each roll, folding it up to only slightly overhang. Next, divvy the caramelized onions among the sandwiches, layering them on the pastrami. Place the Gruyère on the top halves of the rolls. Return the sandwiches, still open-faced, to the oven for 5 minutes, or until the cheese is melted and the pastrami is warm to the touch.
- Sandwich the halves together and, if desired, cut on the diagonal with a serrated knife. You can take it from here. Originally published on February 17, 2013.
Recipe Testers’ Reviews
Each of the individual elements in this sandwich is delicious enough on its own, but together, they’re heavenly, albeit rich. I used a homemade rye bread with a nice crunchy crust and a tight crumb. I didn’t add hot pepper flakes to the caramelized onion because I wanted a purely sweet flavor. The aioli had the perfect amount of garlic—enough so you could taste it in the background but not so much that it overwhelmed the other flavors in the sandwich.
These pastrami, caramelized onion and Gruyère sandwiches were surprisingly rich because of all the strong flavors—I think you could make little mini 1- or 2-bite sandwiches as a perfect hors d’oeuvre! I’ll definitely be making these again when I’m in the mood for a decadent sandwich.
This is a yummy sandwich. We made it on good rye bread and had it for supper. The size of the bread or roll makes a difference here. Our slices of bread were on the small side so we each had two overstuffed sandwiches and enjoyed them to the last bite!
I omitted the red pepper flakes in our sandwiches for the sake of the young eaters. The caramelization of the onions was easy to do and affords the cook the time to make the mustard aioli. When everything is done you can let the aioli flavors meld a little or serve it right up. A quick dinner.
We enjoyed every part of this pastrami, caramelized onion and Gruyère sandwich for lunch. We found the pretzel knot rolls at Whole Foods and they were the perfect combination of crisp outside and soft inside. I made the onions the day before to speed up my day-of assembly. The aioli (my first attempt ever) was easy to make and came together flawlessly, and, of course, how could you go wrong with pastrami and Gruyère?
My only wish was that our pretzel rolls were slightly larger—one was a little small for lunch and yet 2 sandwiches would’ve been too much. Finally, I think these sandwiches could be made in advance and wrapped up to serve later. They’d be just as good at room temp as they are right out of the oven.
What a lovely, gooey, yummy sandwich! Gruyère, peppered pastrami, and caramelized onions make the world go around as far as this tester is concerned. I loved the bite of the pepper, the richness of the Gruyère, and the sweet onions all trying to escape the toasted onion bread I used to surround it. Then add in that wonderful mustard aioli and you really did it to me. Some people would say this is just a sandwich, but me, I say this is dinner for company.