If you have leftover steak from your last barbecue, this steak sandwich with caramelized onions and a creamy horseradish sauce is the perfect way to enjoy the beef.
While we are more burgers and brats type of people when it comes to grilling (and give me ALL the sides!), we do like to grill steaks a few times every summer. Paired with some grilled onions and mushrooms, an ear or two of corn on the cob, and an ice cold beer and I am one happy lady.
Since I tend to overdo it on the sides, I pretty much always have leftover steak. I’m definitely not one to waste a good piece of meat but leftover steak on its own just doesn’t have quite the appeal as the juicy, pink in the middle steak that comes straight off the grill. 
Enter: the steak sandwich. Leftover steak is ideal for a steak sandwich because the key to a good steak sandwich is getting super thin slices of steak. When you cut the steak cold, it’s a lot easier to get thinner slices than when it’s hot. Another pro tip? Cutting against the grain. Obviously.
That said, these Grilled Steak and Onion Sandwiches with Creamy Horseradish Sauce are still 100% delicious with freshly grilled steak.
The star in these sandwiches is definitely the creamy horseradish sauce. I used to be one of those people who “didn’t like horseradish” but really – I just didn’t know what I was talking about. I also used to dip my steak in ketchup.
Anyways, this creamy horseradish dip is pretty much your steak’s new best friend. It’s SO good and SO easy. The base of the sauce is plain yogurt, but you can use sour cream if you please. To the yogurt I added a spoonful of mayo, some garlic, fresh horseradish, and some salt and pepper and holy smokes was it good!
A generous smear of the horseradish sauce on a lightly toasted bun, topped with that thinly sliced steak and grilled onions and you have yourself one delicious spring/summer dinner!
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Horseradish and Grilled Steak Sandwich
- Total Time: 50 minutes
- Yield: Serves 2
- Diet: Omnivore
Description
Leftover steak gets a new life in this creamy, flavorful sandwich. Caramelized onions and a zesty horseradish sauce elevate simple grilled beef.
Ingredients
- 1/2 cups (118 ml) plain yogurt
- 2 tbsp mayonnaise
- 1 tbsp horseradish
- 2 cloves garlic
- 1/4 tsp salt
- 1/4 tsp pepper
- 2 lbs (907 g) sirloin steaks
- Your favorite steak seasoning
- 3 tbsp olive oil
- 2 yellow onions
- 4 ciabatta buns
- Butter
- Arugula
Instructions
For the horseradish sauce
- Combine all sauce ingredients and stir well. Cover and refrigerate until ready to use.
For the steak sandwiches
- Preheat grill over medium-high heat.
- Season steak with steak seasoning and lightly brush with 1 tablespoon of olive oil. Let sit at room temperature for 20 minutes.
- Toss onions with 2 tablespoons olive oil, salt, and pepper. Place in a grilling pan or foil packet.
- Grill onions until softened and caramelized, about 25 minutes.
- Place steak on grill and cook for 4-5 minutes per side, until golden brown and grill marked.
- For medium-rare, cook until 140°F (60°C) internal temperature (another 3-4 minutes). For medium, cook until 150-155°F (66-68°C) (another 5-6 minutes). For medium-well, cook until 160-165°F (71-74°C) (another 6-7 minutes). Use a meat thermometer to ensure desired doneness.
- Let steak rest for 3 minutes before slicing.
- Butter the buns and grill for 1-2 minutes, butter side down, until lightly toasted. Watch closely to prevent burning.
- Cut the rested steak thinly.
- Spread approximately 2 tablespoons of horseradish sauce on the bottom bun.
- Top with steak and onions.
- Top with arugula and the top bun.
- Serve.
Notes
- For a richer flavor, use Greek yogurt instead of plain yogurt in the horseradish sauce.
- To prevent the onions from burning, reduce the heat slightly if they begin to brown too quickly.
- Leftover steak sandwiches can be stored in the refrigerator for up to 2 days. Reheat gently in a pan or microwave.
- Prep Time: 15 minutes
- Cook Time: 35 minutes
- Category: Sandwich
- Method: Grilling
- Cuisine: American
Nutrition
- Serving Size: 1 sandwich
- Calories: 600
- Sugar: 5
- Sodium: 800
- Fat: 35
- Saturated Fat: 15
- Unsaturated Fat: 15
- Carbohydrates: 40
- Fiber: 5
- Protein: 40
- Cholesterol: 100
Frequently Asked Questions
How do I make the creamy horseradish sauce for the sandwich?
To make the creamy horseradish sauce, simply mix prepared horseradish with sour cream, mayonnaise, and a pinch of salt until well combined.
What’s the best way to slice leftover steak for the sandwich?
For the best results, slice the leftover steak cold and against the grain to achieve super thin slices that will fit perfectly in the sandwich.
Can I use freshly grilled steak instead of leftover steak for this recipe?
Yes, you can use freshly grilled steak; just be sure to let it rest for a few minutes before slicing it thinly for the sandwich.
