Steak Crostini with a Creamy Horseradish Sauce and Caramelized Onions

Level up your appetizer game with this Steak Crostini Recipe with creamy horseradish sauce and caramelized onions. 

Crispy baguette toasts get topped with juicy fillet mignon slices, sweet, soft onions and silky horseradish sauce. What I love about these is that you could easily find them served at a wedding, but they’re incredibly simple to make! I like to make them for cocktail parties and special family gatherings. They’re so good that I sometimes make them as part of a little at-home date night menu.

For a spread of elegant appetizers, pair this steak crostini recipe with my chicken spiedini skewers with amogio sauce, these Boursin cheese, caramelized onions, and bacon puff pastry pinwheels and my Sweet potato and goat cheese fall flatbread.

WHY YOU’LL LOVE THIS RECIPE

Once you’ve made these once, you’ll reach for the recipe over and over. Tender and juicy, the seared steak is absolute perfection with the sharp horseradish sauce, sweet onions and crunchy crostini base.

This easy appetizer is one of those perfect holiday appetizers for a crowd. It’s a favorite of mine as far as Christmas holiday appetizers go. I find they disappear really quickly – a testament to how yummy they are. This is the best Steak Crostini Recipe I’ve ever tried, so I hope you love it as much as I do!

WHAT ARE CROSTINI?

Originally Italian, crostini are little toasted bread rounds brushed with olive oil before being baked. They are designed to be bite-sized and hold various toppings.

For easy holiday appetizers, make a big batch of crostini and top them with a variety of ingredients. They make the perfect base in this Steak Crostini Recipe.

WHAT CUT OF STEAK IS BEST FOR STEAK CROSTINI?

Filet mignon or beef tenderloin is ideal for its tenderness. 

You can also make it with sirloin or ribeye – it just needs to be sliced really thin and make sure you rest it after cooking.

INGREDIENTS FOR THIS APPETIZER RECIPE

There are a quite a few ingredients but a lot of them are typical pantry staples”:

• Filet mignon or tenderloin: Choose a good quality cut of meat as the quality really shines through in this Steak Crostini Recipe. I like to use filet at room temperature as it cooks evenly.
• Unsalted butter: Unsalted lets you control the seasoning. You’ll need it for the caramelized onions, too.
• Garlic powder: Using powdered garlic over fresh is easier, as it doesn’t burn as easily as fresh garlic. 
• Dried thyme: Literal perfection with beef.

FOR THE CROSTINI

• Baguette: Choose a narrow, round baguette so your crostini are round and “well-shaped”.
• Olive oil: The flavor of the olive oil is obvious in this steak crostini with caramelized onions, so use a good one.

FOR THE HORSERADISH SAUCE

• Mayonnaise: Use a thick, creamy mayo as it makes up the base of the sauce in this Steak Crostini Recipe.
• Horseradish: You can add more or less, as you like.
• Dijon mustard: Don’t skip it – it adds SO much to the sauce.
• Lemon juice: Use fresh lemon juice to balance the sauce.

FOR THE CARAMELIZED SHALLOTS

• Shallots: You can also use regular onions, but shallots are sweeter and a little milder.
• Balsamic vinegar: Helps balance this recipe and adds sharpness and color.
• Brown sugar: Sweetens up the onions. White sugar can work in a pinch.

• Salt and black pepper: You’ll need to season each component of this recipe with salt and pepper.

Ingredient quantities can be found at the bottom of the article in the recipe card

HOW TO MAKE THIS RECIPE

This is my step by step guide to making the best Steak Crostini Recipe:

Season the steak 

Sprinkle it with salt, pepper, garlic powder, and thyme. Rest the steak for least 30 minutes to absorb the flavors.

Mix the horseradish sauce

In a bowl, combine mayonnaise, horseradish, Dijon mustard, and lemon juice. Season to taste and chill until you need it. 

Sauté the shallots 

Add butter to a saucepan and warm it over medium heat. Add the onions and cook gently until softened. 

Next, add the vinegar, brown sugar, salt, and pepper, then cook until caramelized and golden, about 30 minutes. Set aside.

Sear the steak 

Cook your steak in olive oil over medium-high heat to your preferred doneness. 

Rest before slicing thinly. I like to rest it at least 15 minutes for the juiciest steak.

Make the crostini

Brush baguette slices with olive oil and toast for 5–7 minutes until golden in the oven.

Assemble and garnish

Spread horseradish sauce on crostini, top with steak slices and caramelized shallots. Garnish with fresh herbs like thyme or parsley.

STORAGE AND MAKE AHEAD

If you want to prepare ahead, make each element (steak, sauce, onions, crostini) and store them separately in the refrigerator. Up to 48 hours ahead is great! 

In this case, I suggest storing the steak whole and only slicing it when you’re ready to assemble your Steak Crostini Recipe.

You can make the crostini ahead of time. If I make them a few days ahead, I like to pop them back into the oven to crisp them up (for a few minutes) before serving them.

Here are my 6 top tips for the best Steak Crostini Recipe:

1. Rest your steak: This has got to be my number 1 top tip. Resting the meat allows it to draw back its juices so it turns out butter-tender.
2. Use day-old bread: Yup! It toasts up crispier than fresh bread.
3. Slice the steak thinly: I like to slice it against the grain and thinly – it makes the eating experience more “elegant”.
4. Prep ahead: Save yourself some stress and get your onions and sauce made a day or two ahead.
5. Watch the shallots closely: They burn in seconds so keep an eye on them.
6. Garnish with something fresh: Like thyme, parsley, or chives. This recipe is quite decadent and fresh herbs help balance the flavors. They also look pretty!

FREQUENTLY ASKED QUESTIONS

OTHER ELEGANT APPETIZER RECIPES TO TRY

For more delicious appetizer ideas, try one or a couple of these. They all make elegant Christmas appetizers.

• Baked crabby bread
• Boursin cheese topped with caramelized onions and crispy bacon
• Crispy rice topped with crab rangoon
• Whipped feta and cottage cheese with balsamic strawberries on toasted garlic bread
• Watermelon bruschetta with whipped feta

Steak Crostini with a Creamy Horseradish Sauce and Caramelized Onions

Taylor Jackzen

You've got to try this pretty and utterly delicious Steak Crostini recipe. The sweet onions, tender steak, creamy and light horseradish sauce on top of crusty crostini is pure perfection. This is a great holiday appetizers make ahead idea!

Print Recipe Pin Recipe

Prep Time 30 minutes mins

Cook Time 40 minutes mins

Total Time 1 hour hr 10 minutes mins

Course Appetizer

Servings 12

Ingredients

  

For the Steak

• 1 pound filet mignon or tenderloin
• Salt and black pepper to taste
• 2 tablespoons unsalted butter
• 1 teaspoon garlic powder
• 1 teaspoon dried thyme

For the Crostini

• Baguette thinly sliced
• Olive oil for brushing

For the Horseradish Sauce:

• 1/2 cup mayonnaise
• 2 tablespoons horseradish
• 1 tablespoon Dijon mustard
• 1 tablespoon lemon juice
• Salt and black pepper to taste

For the Caramelized Shallots

• 2 tablespoons unsalted butter
• 2 large shallots thinly sliced
• 1 tablespoon balsamic vinegar
• 1 tablespoon brown sugar
• Salt and black pepper to taste

Instructions

 

• Season the steak with salt, black pepper, garlic powder, and dried thyme. Ensure the steak is well coated. Let it sit for at least 30 minutes.
• In a small bowl, mix together mayonnaise, prepared horseradish, Dijon mustard, and fresh lemon juice. Season with salt and black pepper. Refrigerate until ready to use.
• In a skillet over medium heat, melt butter. Add thinly sliced shallots and cook until softened, stirring occasionally.
• Add balsamic vinegar, brown sugar, salt, and black pepper. Continue cooking until the shallots are caramelized and golden brown (the caramelizing process should take about 30 minutes in total). Remove from heat and set aside.
• Heat olive oil in a skillet over medium-high heat. Cook the steak according to desired doneness on each side. (I used Filet Mignon and cooked mine for 4 minutes on each side for a medium-rare). Remove from heat and set aside to rest.
• Preheat the oven to 375°F (190°C).
• Brush the baguette slices with olive oil and place them on a baking sheet. Toast in the oven for 5-7 minutes or until golden brown.
• Slice the steak into thin strips.
• Spread a layer of creamy horseradish sauce on each toasted baguette slice.
• Top with a slice of cooked steak and a spoonful of caramelized shallots.
• Arrange the steak crostini bites on a serving platter and garnish with fresh thyme or parsley if desired.
• Serve immediately and enjoy your delicious steak crostini bites with creamy horseradish sauce and caramelized shallots!