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French Onion Steak Sandwiches

French Onion Steak Sandwiches are an easy-to-make, delicious choice to serve for a family-friendly dinner.

french onion steak sandwiches on white plate

You probably forget that making sandwiches for dinner is a perfectly acceptable option. Here’s a reminder! These fabulous French Onion Steak Sandwiches are stuffed with perfectly seasoned, caramelized onions, sliced sirloin steak, melted Gruyere cheese and simply dressed lemon arugula. These flavors all come together to create one delicious sandwich that everyone will love.

secret ingredient cookbook cover

The Secret Ingredient Cookbook by Kelly Senyei

This recipe comes from a new cookbook by Kelly Senyei from the Just a Taste blog: The Secret Ingredient Cookbook. This book is full of tasty recipes that each have a “secret ingredient” that boosts the flavor and uniqueness of the recipe. Example: for the Sweet and Tangy Baked Chicken Wings recipe, the secret ingredient is blackberry jam! This book is full of family-favorite, delicious recipes. It’s a must-have new cookbook for your cookbook shelf.

Here are a few recipes we have bookmarked to make:

  • Berry Breakfast Pastries
  • Blueberry French Roast Muffins
  • Sheet Pan Barbecue Meatballs
  • Soupy Thai Chicken Noodles
  • Shrimp Scampi Linguine
  • Sticky Pineapple Chicken
  • Baked Chicken Tenders with Honey Mustard Sauce
  • The Chocolate Chip Cookies
  • Raspberry Chocolate Sheet Cake
  • Hot Chocolate

ingredients displayed for making french onion steak sandwiches

Ingredients needed:

  • butter
  • onions
  • onion soup mix
  • sirloin steak
  • kosher salt and freshly ground black pepper
  • olive oil
  • French sandwich rolls
  • Gruyere cheese
  • lemon juice
  • arugula

How to make French Onion Steak Sandwiches:

For the complete, printable recipe with all ingredients and instructions, scroll to the end of this post.

Onions are sautéed in butter until they are golden. Then you’ll add in the secret ingredient: a package of onion soup mix. The softened onions are sautêed more until they are dark brown and caramelized.

The steaks are seasoned with salt and pepper and pan-fried until done. Then the steaks are sliced thinly.

two photos showing assembly of french onion steak sandwich

Preheat the oven to broil. Divide the caramelized onions between 4 French rolls, spreading the onions on the bottom half of each roll. Lay the steak slices on top of the onions, and top with shredded Gruyere cheese. Place under the broiler to melt the cheese. Top with lemon-juice dressed arugula.

steak sandwich on long roll on white plate

Top with the other half of the bun to finish up these French Onion Steak Sandwiches. They’re ready for serving!

french onion steak sandwiches on white plate

Slice them in half. I suggest serving them with our Watermelon Strawberry Caprese Salad or this Butter Leaf Lettuce Summer Salad for the perfect balance of a light pairing.

hand holding steak sandwich

Thanks to Kelly Senyei for this great recipe from The Secret Ingredient Cookbook. I think you’re going to love this cookbook, and these French Onion Steak Sandwiches are a great recipe to start with. Enjoy!

french onion steak sandwiches on white plate

French Onion Steak Sandwiches (shared from The Secret Ingredient Cookbook by Kelly Senyei)
The caramelized onions on these sandwiches are boosted with a secret ingredient!
Prep Time 20 minutes
Cook Time 1 hour 20 minutes
Total Time 1 hour 40 minutes
Course Sandwiches
Cuisine American
Servings 4 servings
Calories 470 kcal



  • 2 tablespoons unsalted butter
  • 2 medium white onions, thinly sliced
  • One 1-ounce package onion soup mix




  • Heat the butter in a large skillet set over medium heat. Once the butter has melted, add the onions and cook, stirring occasionally, for 20 minutes, until the onions soften and become golden. Reduce the heat to medium-low, then stir in the onion soup mix. Cook the onions, stirring as needed to prevent burning, until they are dark brown and caramelized, about an additional 30 minutes. If at any point the onions begin to burn, add 2 tablespoons of water to the pan and continue cooking. Set the onions aside.


  • Season the steaks with salt and pepper. Coat the bottom of a large skillet set over medium-high heat with olive oil. Once the skillet is hot, add the steaks and cook to your desired doneness. For medium-rare, cook for about 8 minutes, or until they reach an internal temperature of 130℉.
  • Transfer the steaks to a cutting board and let them rest for 10 minutes. Slice the steaks as thinly as possible against the grain.


  • Preheat the oven to broil. Place the four bottom halves of the sandwich rolls on a baking sheet, then divide the caramelized onions among the rolls. Top the onions with the steak and Gruyere cheese. Place the sandwiches about 4-inches under the broiler and broil until the cheese is melted.
  • In a medium bowl, whisk together 2 teaspoons of olive oil and the lemon juice. Add the arugula and a pinch of salt and pepper, then toss to combine. Top the sandwiches with arugula, then add the top halves of the rolls and serve.


Serving: 1servingCalories: 470kcalCarbohydrates: 43gProtein: 27gFat: 21gSaturated Fat: 10gPolyunsaturated Fat: 1gMonounsaturated Fat: 6gTrans Fat: 0.2gCholesterol: 75mgSodium: 1095mgPotassium: 387mgFiber: 3gSugar: 7gVitamin A: 639IUVitamin C: 7mgCalcium: 303mgIron: 12mg
Keyword french onion, sandwiches, steak
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