Steak Sandwich Recipe

Place the shaved sirloin in a large bowl. Add the Korean kalbi sauce, 1 tbsp neutral oil, 1 tsp kosher salt, and 1 tsp black pepper. Toss to coat evenly, massaging the sauce into the meat. Let marinate at room temperature for 10–15 minutes (or refrigerate up to 2 hours).

Heat a large cast-iron skillet or heavy sauté pan over high heat until very hot. Add the marinated beef in a single layer (work in batches if needed) and sear, stirring and spreading pieces so they cook quickly, about 2–4 minutes per batch until browned and just cooked through. Remove to a plate and tent loosely with foil.

While the steak rests, wipe the skillet (or use a separate large skillet) and add 1 tbsp olive oil and 2 tbsp butter over medium heat until foam subsides.

Add the thinly sliced onions, toss to coat, and cook gently over medium-low heat, stirring occasionally, until they begin to soften and turn golden, about 12–18 minutes. Sprinkle 1 tsp brown sugar over the onions 8–10 minutes in to help with caramelization.

When onions are lightly caramelized, push them to one side of the pan. Add the sliced mushrooms to the cleared area, increase heat to medium-high, and cook mushrooms without stirring for 2 minutes to develop color, then stir and cook another 3–4 minutes until browned and their liquid has mostly evaporated.

Combine mushrooms and onions, add 1 tsp apple cider vinegar, 1/2 tsp kosher salt, and 1/4 tsp black pepper. Stir and cook another 1–2 minutes to meld flavors. Taste and adjust seasoning. Keep warm.

In a small bowl combine 1/2 cup mayonnaise, 3 tbsp finely chopped scallions, 1 tsp lemon juice, 1 minced garlic clove, 1/2 tsp sesame oil, 1/4 tsp salt, and 1/8 tsp black pepper. Whisk until smooth and taste; adjust acidity or salt as needed. Chill until assembly.

Slice the schiacciata rolls in half horizontally. Spread a thin layer of butter on the cut sides.

Heat a clean skillet or griddle over medium-high heat. Toast the buttered cut sides of the bread face-down until golden brown and crisp, about 1–2 minutes.

Spread about 1 tbsp scallion aioli on both bottom and top halves of each roll. Pile a generous portion (about 1/4 lb worth) of the cooked kalbi-marinated shaved sirloin onto the bottom halves.

Top the steak with a spoonful (about 2–3 tbsp) of the warm caramelized onions and mushrooms, scatter cilantro leaves (about 2 tbsp per sandwich), and add optional pickled jalapeños if using.

Close sandwiches, press gently, slice in half if desired, and serve immediately while warm.