Skirt Steak Sandwich

PREP TIME	REST TIME	COOK TIME
30 mins	0 to 4 h	1 hour 15 mins

This skirt steak sandwich is simple, fast, and ridiculously good. You can cook the steak fresh in a hot pan or use the leftovers; either way, it comes out amazing. Think crusty ciabatta, thin slices of skirt steak with that deep brown crust and perfectly pink inside, provolone melting over the top, caramelized onions, sauteed mushrooms, a bit of arugula, and mustard aioli to pull it all together. Juicy, salty, rich, and messy in the best way possible.

Since the onions take quite a while to cook, it’s a good idea to prepare larger batches of caramelized onions and sauteed mushrooms and keep them in the refrigerator for a few days. That way, you’ll have them ready to go for another steak sandwich or whatever else you want to make later. That’s what I usually do. I just double or even triple the amounts from the recipe, so I don’t have to cook them again every time. Since caramelized onions can take about 45-60 minutes to cook, it saves a lot of time to have them ready in advance. Then I just reuse them to make the same sandwich again, or tweak it with different cheese, steak, sauce, or use them in a completely different steak sandwich recipe. If you’re already spending this much time making caramelized onions, I highly recommend making extra.

In this recipe, I also show you how to pan-sear a perfect skirt steak, but if you prefer, you can cook it your own way or use leftovers. Honestly, you can make this sandwich with any steak. Just make sure to stick with tender, flavorful cuts for the best results.

The Ingredients You’ll Need

For Steak:

• Skirt steak: 1 to 1½ pounds (454 to 680 grams). Use outside skirt steak, not inside skirt. The outside skirt is more tender, flavorful, and juicy. It doesn’t need a marinade, just salt and pepper, like any other premium, well-marbled cut.
• Kosher salt: As a general rule, use about 1% of the steak’s weight, or up to 1.5% if you want a deeper, more seasoned flavor. Always go with kosher salt. It spreads evenly and gives you much better control than regular table salt.
• High-smoke-point oil: 1–2 tablespoons (15–30 ml). I prefer the refined avocado oil. It’s neutral in flavor and has a high smoke point (around 500°F / 260°C), which makes it perfect for pan-searing over high heat.

For the Caramelized Onions:

• Oil: 3 tablespoons (45 ml). I use the same oil I use for pan-searing the skirt steak and sauteing mushrooms (refined avocado oil). For onions, you don’t need a high-smoke-point oil; olive oil works fine here if that’s what you prefer.
• Onions: About 1½ pounds (680 grams) of large, peeled and finely sliced onions (preferably yellow onions). Double the amount if you want to make a larger batch and keep some in the fridge or freezer for later.
• Kosher salt: 1/2 teaspoon (2-3 g). Add it at the beginning; it adds flavor and draws out the onions’ moisture faster, slightly speeding up the caramelizing process.

For the Sauteed Mushrooms:

• Mushrooms: 1/2 pound (about 227 g). I usually go with white mushrooms, but use whatever you like. Like with the caramelized onions, double the amount if you want to make a larger batch and store some in the fridge or freezer for later.
• Oil: 2 tablespoons (30 ml). I use the same oil I use for pan-searing the skirt steak. You don’t need a high-smoke-point oil; you can use, for example, olive oil or canola oil.

For Mustard Aioli Sauce:

• Mayonnaise: 1 cup (about 220-240 g). If you like, you can make homemade mayonnaise, but store-bought works just as well.
• Mustard: 2 tablespoons (30 g). I prefer Dijon mustard, but you can use any type you like.
• Lemon juice: 1 tablespoon (15 ml). Always use fresh lemon juice for the best flavor.
• Garlic: 2 cloves, finely chopped, grated, or minced. Use whatever method fits you best. All we need is garlic in a fine, granular form. You can also use about 1/2 teaspoon of garlic powder if you don’t have fresh garlic.
• Kosher salt: to taste, about 1/2 teaspoon (about 3 g).

For Sandwich:

• Ciabatta rolls: About 4–8 small to medium rolls (around 50–125 g each). In total, you’ll need about 400–500 g of bread for this recipe. I prefer ciabatta, but you can use a different type of bread if you like (such as a baguette).
• Cheese: Provolone cheese, about 4 ounces (113 g), sliced thin. Use just enough to cover the bread with at least one layer, or more, depending on your roll size. I like provolone, but you can use any cheese you prefer; American, Swiss, or even blue cheese all work great.
• Arugula: About 50 g of fresh arugula. Greens pair perfectly with steak sandwiches. Alternatively, you can use spring mix or any other salad greens you like.

How to Make Skirt Steak Sandwich – Step by Step Photos

This recipe requires some time, but overall, it’s quite simple. Most of the steps can be done while the onions are caramelizing. Alternatively, you can do the time-consuming steps (caramelizing the onions and sauteing the mushrooms) ahead of time, then finish everything the next day in 20–30 minutes.

Follow the steps below and do them in a way that works best for you.

Step 1: Prepare the Skirt Steak

Pat the skirt steak dry with paper towels and trim off any excess fat. If it’s a whole, long piece, cut it into smaller steaks about 4–6 inches (10–15 cm) long (see note below for why this helps).

Once the steaks are ready, season both sides lightly with kosher salt (not too much, since skirt steak is a relatively thin cut). Place them on a wire rack set over a baking sheet, then refrigerate uncovered for 2–4 hours. Remove the steaks from the refrigerator at least 20 minutes before cooking and let them rest at room temperature. While the steaks rest, prepare the caramelized onions, sauteed mushrooms, and mustard aioli.

Step 2: Caramelize the Onions

Trim off the top and root ends of the onions, then cut them in half. Peel them, remove the first outer layer, and place each half flat-side down. Slice them finely. Heat a 10– to 12-inch (25– to 30–cm) skillet over medium heat for about 1-2 minutes. Then, add the oil and let it heat for an additional minute. Once the oil is hot and shimmering, add the onions and salt.

Saute for about 3 minutes, stirring occasionally, until they start to soften. Then reduce the heat to medium-low and keep cooking, stirring every few minutes, until the onions are very soft and deep golden brown. If they start sticking to the bottom or look like they might burn, add about 1 tablespoon (15 ml) of water, scrape up the browned bits with a spatula, and continue cooking. Add a little more water whenever needed to prevent burning.

The total cooking time depends on the amount of onions you’re using and your stove, but for about 1.5 pounds (680 g) of onions, it usually takes around 45-60 minutes. While the onions cook, I recommend making the mustard aioli sauce first, then sauteing the mushrooms in another pan. It’ll save you a lot of time overall.

Step 3: Saute the Mushrooms

Slice the mushrooms into 1/4 to 1/2 inch (0.6–1.3 cm) thick pieces. Heat a skillet over medium-high heat for 1–2 minutes, then add 2–3 tablespoons of oil. Let the oil heat for about a minute, then add the mushrooms. Cook them, stirring occasionally, until they’re soft and browned all over (about 15 minutes). Once done, remove the mushrooms from the pan and set them aside in a container for later.

Step 4: Make the Mustard Aioli Sauce

Combine all the ingredients in a small bowl: 1 cup of mayonnaise, 2 tablespoons of mustard, 1 tablespoon of fresh lemon juice, and 2 garlic cloves (finely chopped, grated, or minced). Season with kosher salt to taste, then set the sauce aside for later use.

Step 5: Pan-Sear the Skirt Steak

If you’ve refrigerated the salted steak, take it out at least 20 minutes before cooking. Once it’s ready, preheat a skillet (preferably a cast-iron skillet) over medium-high heat for 3 minutes. Add the oil and let it heat for about 1 minute. Once the pan is hot and the oil is shimmering, pat the skirt steak dry again with paper towels. Next, carefully place the steak in the pan and start searing.

For steaks about 1/2–1 inch (1.3–2.5 cm) thick, cook while flipping every 30 seconds. Use a meat thermometer and remove the steak when it’s about 10–15°F (5–8°C) below your target doneness (see the temperature chart below). Let it rest for about 5 minutes. These typically take 3–6 minutes in total to reach medium-rare to medium, depending on the thickness.

For thinner cuts (1/2 inch / 1.3 cm or less), flip every 30 seconds and slide the steak around the pan every 15 seconds to move it over hotter spots (this helps build a better crust). Since it’s hard to use a thermometer on thinner pieces, rely on timing instead. These cook quickly: about 60–90 seconds total for 1/4-inch (0.6 cm) steaks, or 2–3 minutes for 1/2-inch (1.3 cm) steaks. Remember to let the steak rest for 5 minutes after removing it from the pan.

Doneness	Remove at temp:	Final temp:
Rare	105–115°F (40–46°C)	120–130°F (49–54°C)
Medium Rare	115–125°F (46–52°C)	130–140°F (54–60°C)
Medium	125–135°F (52–57°C)	140-150˚F (60–66°C)
Medium-Well	135–145°F (57–63°C)	150-160˚F (66–71°C)
Well Done	145–155°F (63–68°C)	160°F+ (71°C+)

Step 6: Assemble the Skirt Steak Sandwich

Once the steak has rested, slice it very thinly against the grain (see note below). Cut the ciabatta rolls in half lengthwise. Place both the bottom and top halves on a baking sheet lined with foil or parchment paper. Spread a layer of mustard aioli on the bottom halves, then add the sliced steak. Evenly distribute the caramelized onions and sauteed mushrooms on top, then add the cheese.

Keep the sandwiches open and place them in the oven, as close to the heating element as possible. Bake for about 3–5 minutes, just until the cheese melts and the top halves of the ciabatta toast up nicely. Then spread a little mustard aioli on the top halves, add the arugula, and close the sandwiches. Serve right away while everything’s still warm.

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More Steak Recipes To Try

• Garlic Butter Steak Bites
• Cast Iron Skillet Steak
• Garlic Butter Steak and Potatoes Skillet