Mushroom Swiss Recipe

Prep

Thinly slice the steak if not pre-sliced; pat dry and season lightly with 1/4 tsp salt and 1/4 tsp pepper. Clean mushrooms with a damp towel and slice 1/4-inch thick. Thinly slice the onion and mince the garlic. Split the rolls lengthwise but keep hinge intact if desired.

Cook mushrooms and onions

Heat 1 tablespoon olive oil and 1 tablespoon butter in a large skillet over medium-high heat until shimmering. Add the sliced onions and cook, stirring occasionally, for 4–5 minutes until they begin to soften. Add the sliced mushrooms and continue to sauté for 6–8 minutes until mushrooms release their liquid and it evaporates and both are golden-brown. Stir in the minced garlic and thyme and cook 30 seconds more until fragrant. Season with 1/4 tsp salt and 1/4 tsp pepper. Transfer the mushroom-onion mixture to a bowl and set aside.

Cook the steak

In the same skillet, add the remaining 1 tablespoon butter and raise heat to medium-high. Add the thinly sliced steak in a single layer (work in batches if needed) and sear quickly for 45–60 seconds per side until browned but still tender. Sprinkle with remaining 1/4 tsp salt and 1/4 tsp pepper while cooking. Remove the steak and set aside with the mushrooms.

Make pan sauce

Lower heat to medium and return the skillet to the stove. If bits are sticking, add the beef broth to deglaze the pan, scraping browned bits with a spatula. Stir in Worcestershire sauce, Dijon mustard, and soy sauce. If you want a slightly thicker sauce, whisk 1 tsp flour into the broth before adding or sprinkle the flour into the pan and cook 30 seconds. Simmer the sauce for 2–3 minutes until slightly reduced. Taste and adjust seasoning with up to 1/4 tsp salt and more pepper if needed. Return the steak and mushrooms to the skillet and toss to coat in the sauce for 1 minute.

Assemble and melt cheese

Preheat the broiler or an oven set to 450°F (230°C). Lightly butter cut sides of the rolls and place cut-side up on a baking sheet. Toast under the broiler for 1–2 minutes until lightly golden (watch closely). Distribute the steak-mushroom mixture evenly among the 4 rolls. Top each with a slice (or folded slices) of Swiss cheese. Place the sandwiches back under the broiler or into the oven for 1–2 minutes until the cheese is melted and bubbling.

Finish

If using mayonnaise, spread 1 tsp on the top roll before closing. Close the sandwiches and let rest 1 minute. Serve hot with any remaining pan sauce spooned over the filling, and optional pickles or crispy fries on the side.