A perfect balance of smoky, tender steak, rich caramelized onions, and creamy horseradish sauce—this French Onion Steak Sandwich is a true indulgence. Whether you’re preparing it for a special dinner or just craving something flavorful and hearty, this recipe will satisfy your taste buds. Melted Swiss cheese, savory steak, and the deep flavor of slow-cooked onions are all sandwiched in a toasted French bun, making each bite irresistible.

Ingredients

For the Creamy Horseradish Sauce:

• 1/2 cup mayonnaise
• 1/2 cup sour cream
• 1 tablespoon prepared horseradish sauce
• 1 tablespoon Dijon mustard
• Juice from 1 lemon
• Zest of 1/2 lemon
• 2 teaspoons fresh rosemary, finely chopped
• 2 teaspoons fresh chives, finely chopped
• 1 teaspoon freshly ground black pepper

For the French Onions:

• 2 large white onions, diced
• 6 cloves garlic, minced
• 1 cup beef broth
• 3 tablespoons dark lager beer
• 1 tablespoon fresh rosemary, finely chopped
• 2 teaspoons kosher salt
• 2 tablespoons beef tallow (or substitute with butter)
• 1 tablespoon fresh parsley, finely chopped

For the Steak:

• Olive oil (for coating)
• Binder (optional, such as mustard or oil)
• Steak King seasoning (or your preferred steak seasoning)

For Assembling the Sandwiches:

• French sub buns
• 6 slices Swiss cheese (per sandwich)
• Hickory wood chunks (for smoking the steaks)

Instructions

1. Prepare the Creamy Horseradish Sauce:
Start by mixing together the creamy components of the sandwich. In a medium-sized bowl, combine mayonnaise, sour cream, horseradish sauce, Dijon mustard, lemon juice, lemon zest, rosemary, chives, and black pepper. Stir until well-combined, then cover and refrigerate to allow the flavors to meld together. The horseradish sauce can be made a day in advance to intensify the flavor.

2. Cook the French Onions:
The caramelized onions are the heart of this sandwich.

• Heat beef tallow in a large skillet over medium heat. Add the diced onions and sauté for about 15 minutes, stirring occasionally, until the onions soften and start to brown.
• Stir in the minced garlic and kosher salt. Continue cooking for another 30 minutes, stirring frequently, until the onions are fully caramelized and golden brown.
• Once the onions are deeply caramelized, pour in the beef broth and dark lager beer. Let this simmer on low heat for 20-30 minutes until the liquid has reduced and thickened.
• Add the chopped rosemary and parsley, cooking for an additional 10 minutes to infuse the flavors. Once done, set the onions aside.

3. Smoke and Sear the Steak:
The steak’s smoky flavor is enhanced by the slow smoking process.

• Coat the steaks with olive oil and binder (if using). Generously season the steaks with Steak King seasoning or your favorite steak seasoning.
• Preheat your smoker to 250°F (121°C) and add hickory wood chunks for extra smoky flavor. Smoke the steaks until they reach an internal temperature of 118°F (48°C), about 45-60 minutes depending on the thickness of the steak.
• Once smoked, sear the steaks for 60–90 seconds on each side in a hot skillet or grill to create a flavorful crust.
• Let the steaks rest for 8–10 minutes before slicing them thinly against the grain.

4. Assemble the Sandwiches:

• Toast the French sub buns in a preheated oven at 375°F (190°C) for about 5 minutes or until golden and crisp.
• Spread a generous layer of creamy horseradish sauce on the bottom half of each toasted bun.
• Place 3 slices of Swiss cheese on top of the horseradish sauce.
• Add a generous portion of the thinly sliced steak on top of the cheese.
• Layer 3 more slices of Swiss cheese on top of the steak, then spoon on a hearty portion of the prepared French onions.
• Cap with the top half of the toasted bun.

5. Bake the Sandwiches:

• Preheat your oven to 425°F (218°C).
• Place the assembled sandwiches on a baking sheet and bake for 8–10 minutes, or until the cheese is melted and bubbly, and the sandwich is heated through.

6. Serve and Enjoy:
Remove the sandwiches from the oven, slice them in half, and serve while hot. These sandwiches are perfect for a filling lunch or dinner, and they’re sure to impress anyone you serve them to!

Tips for the Best French Onion Steak Sandwich:

• Steak Selection: For the best results, choose a cut of steak that has great flavor and tenderness, such as ribeye, New York strip, or flank steak.
• Cheese Swap: If you’re not a fan of Swiss cheese, Gruyère or provolone would also work wonderfully.
• Make it Ahead: You can prepare the French onions and horseradish sauce in advance to save time when assembling the sandwiches.
• Flavor Variations: For extra flavor, consider adding a drizzle of balsamic glaze or a handful of arugula to the sandwich for some tang and freshness.

Conclusion

This Ultimate French Onion Steak Sandwich is a symphony of flavors and textures, from smoky steak to creamy horseradish and sweet caramelized onions. Whether you’re hosting a gathering or simply craving a flavorful, filling meal, this sandwich will take your taste buds on an unforgettable journey. Enjoy it with your favorite side dish, a cold beer, or a glass of red wine for a meal that’s sure to satisfy.