I use low iron as an excuse to eat steak every week. All I have to do is pick one up from the grocery store and sit it out on the counter, Kris will meander into the kitchen and know what to do. For this one, he knew it would be going into a sandwich and getting toasted so he erred on the side of undercooked (we both prefer ours rare).
One bite had us both saying “wow wow wow wow” for 15 minutes.
This sandwich has everything I want in one bite: juicy ribeye, jammy caramelized onions, melted provolone, peppery arugula, and a creamy horseradish-Dijon sauce on a warm baguette.
You can absolutely stop there, but if you want to take it one step further, use the steak drippings to make a quick mushroom-shallot pan sauce for dipping. This took it over the top!!!
Time: About 1 hour
Serves: 2 generously
Ingredients
For the Steak + Sandwich
1 lb ribeye steak
Kosher salt
Freshly cracked black pepper
1 tablespoon avocado oil
1 tablespoon cold butter
1 baguette
Salted butter, for the bread
3 slices provolone
2 cups arugula
Squeeze of fresh lemon juice
Drizzle of olive oil
For the Caramelized Onions
1 large sweet onion, thinly sliced
1–2 tablespoons butter or olive oil
Pinch of salt
Water, as needed for deglazing
For the Horseradish Dijon
2 tablespoons mayonnaise
1 1/2 tablespoons Dijon mustard
1 1/2 tablespoons prepared horseradish
1 tablespoon finely sliced chives
Optional Mushroom Pan Sauce
1 shallot, finely diced
1 cup mushrooms, diced or thinly sliced
1/2 cup beef or chicken stock, plus more as needed
2 tablespoons heavy cream
1 tablespoon cold butter
Freshly cracked black pepper
Chopped chives, optional
Instructions
1. Season the Steak
Generously salt both sides of the ribeye.
Set the steak on a wire rack while you caramelize the onions. This gives the salt a little time to season the meat and takes some of the chill off the steak before it hits the pan.
For an even better steak: dry brine it ahead of time. Salt the steak on both sides, place it uncovered on a wire rack set over a plate or sheet pan, and refrigerate for anywhere from a few hours to overnight. Remove it from the refrigerator while you caramelize the onions.
2. Caramelize the Onions
Thinly slice the sweet onion.
Add the onion to a large skillet with 1–2 tablespoons butter or olive oil and a pinch of salt.
Cook over medium-low heat for about 30–45 minutes, stirring every few minutes.
The goal is low and slow. The onions will first soften and turn translucent, then gradually become golden, deep brown, and jammy.
If the bottom of the pan starts getting too dry or browned bits begin sticking, add a small splash of water and scrape everything up. Continue cooking until the onions are very soft, sweet, and deeply caramelized.
Transfer to a bowl and set aside.
There’s no need to add brown sugar or balsamic vinegar here — the onions will become plenty sweet on their own with enough time.
3. Cook the Steak
Pat the steak very dry on both sides with paper towels.
Return the skillet to the stove and increase the heat to medium. Add 1 tablespoon avocado oil.
Once the oil is hot, add the ribeye and sear for roughly 3–4 minutes on the first side without moving it.
Flip and cook for another 3–4 minutes, adjusting slightly depending on the thickness of your steak.
Because the sliced steak will go back into a 425°F oven with the sandwich, you want to err on the side of undercooking it during this step.
For a medium-rare finished sandwich, I like to pull the steak when the center is around 115–120°F. It will continue cooking as it rests and again when the sandwich goes into the oven.
Transfer the steak to a cutting board and immediately top with 1 tablespoon cold butter.
Let rest for 10 minutes before slicing.
4. Optional: Make the Mushroom Pan Sauce
While the steak rests, reduce the skillet heat to medium-low.
Add the shallot and mushrooms directly to the steak pan. There should be enough rendered fat left behind to cook them, but add a small drizzle of oil or butter if the skillet looks dry.
Cook for about 5–7 minutes, stirring occasionally, until the mushrooms have released their moisture and begun to brown and the shallot is soft.
Pour in 1/2 cup stock and scrape up all of the browned bits from the bottom of the pan.
Bring to a gentle simmer and reduce by about half.
Add 2 tablespoons heavy cream and stir. If the sauce becomes too thick, add another splash of stock.
Turn off the heat and finish with freshly cracked black pepper and 1 tablespoon cold butter, swirling until glossy.
Add chopped chives if you like.
Keep warm for serving.
5. Make the Horseradish Dijon
In a small bowl, combine:
2 tablespoons mayonnaise
1 1/2 tablespoons Dijon
1 1/2 tablespoons horseradish
1 tablespoon finely sliced chives
Mix until smooth and set aside.
6. Prep the Arugula
Add the arugula to a small bowl with a squeeze of lemon juice, a light drizzle of olive oil, and a pinch of black pepper.
Toss lightly to coat.
7. Assemble the Sandwich
Preheat the oven to 425°F.
Slice the baguette lengthwise.
Spread a thin layer of salted butter over the inside of the bottom half.
Top with a generous layer of caramelized onions.
Slice the rested ribeye against the grain into strips about 1 cm thick and arrange them over the onions. If the cutting board has juices leftover from the steak, use the top half of the baguette to soak them up.
Top the steak with 3 slices provolone.
Place both halves of the sandwich on a baking sheet and bake for about 8–10 minutes, just until the cheese is completely melted and the bread is warm and lightly crisp.
Keep an eye on the steak — remember, it’s continuing to cook during this step.
8. Finish + Serve
Spread the horseradish-Dijon sauce generously over the inside of the top half of the baguette.
Pile the dressed arugula over the warm steak and melted cheese.
Close the sandwich, press gently, and cut down the center.
Serve immediately, with the mushroom pan sauce on the side for dipping if you made it.
Tips
Undercook the steak slightly. This is the biggest thing to remember. The ribeye gets two rounds of heat — first in the skillet and again in the oven — so cooking it perfectly in the skillet usually means overcooking it by the time the sandwich is ready.
Slice against the grain. This makes a huge difference in a steak sandwich. Shorter muscle fibers = much more tender bites.
Don’t rush the onions. True caramelized onions don’t need sugar. Give them low heat and 30–45 minutes and their natural sugars will do the work.
Use the fond. If you make the pan sauce, all of those browned steak bits stuck to the skillet are exactly what you want. Stock loosens them and turns them into the base of the sauce.