Steak Sandwich Recipe

Bring steak to room temperature

Remove the 6 oz striploin from the refrigerator 20–30 minutes before cooking and pat dry with paper towels.

Season

Season both sides evenly with 1/2 tsp kosher salt and 1/4 tsp black pepper.

Sear

Heat a heavy skillet (cast-iron preferred) over medium-high heat until very hot. Add 1 tablespoon vegetable oil. When oil is shimmering, place steak in pan and sear undisturbed for 2–3 minutes until a brown crust forms. Flip and add 1 tablespoon unsalted butter. Continue cooking 2–3 minutes for medium-rare (internal ~130°F/54°C) or longer to desired doneness, spooning melted butter over the steak as it finishes.

Rest and slice

Transfer steak to a cutting board, tent loosely with foil and rest 5–7 minutes. Slice thinly across the grain into 1/4-inch slices. Lightly brush with 1/2 tsp olive oil to keep moist.

Cook onions and mushrooms

While steak rests, heat a medium skillet over medium heat. Add 1 tsp olive oil and 1 tsp butter. Add the 1/2 cup thinly sliced onion and sauté 3–4 minutes until translucent. Add 3/4 cup sliced mushrooms, 1/2 tsp thyme, 1/4 tsp salt and 1/8 tsp pepper. Cook, stirring occasionally, 5–6 minutes until mushrooms are browned and onions caramelized. Adjust seasoning. Keep warm.

Prepare garlic butter

Mix 2 tablespoons softened butter with minced garlic (1 clove) and a pinch of salt.

Toast baguette

Preheat broiler or skillet. Split baguette lengthwise and spread garlic butter on cut sides. Toast under broiler 1–2 minutes or in a skillet, cut-side down, until golden and fragrant. Remove and spread Dijon mustard (1 tablespoon) on the bottom half.

Cook fries

Cook 2 cups frozen French fries according to package instructions (or for fresh fries: toss 2 cups cut russet fries with 1 tablespoon oil and 1/2 tsp salt and roast on a baking sheet at 425°F/220°C for 25–30 minutes, turning once, until golden and crisp). Keep hot.

Assemble sandwich

On the mustard-spread bottom baguette, layer half of the sliced steak, top with half the sautéed mushrooms and onions, then add remaining steak slices if desired. Place the top garlic-toasted baguette half over the filling. Lightly press and slice in half if serving.

Plate

Serve the sandwich immediately with a side of hot French fries. Garnish fries or sandwich with optional chopped parsley (1 tsp).