Dinner

Steak Crostini with Creamy Horseradish Sauce and Caramelized Shallots Recipe

ByLila Prescott November 27, 2025November 27, 2025

Introduction

Steak Crostini with creamy horseradish sauce and caramelized shallots makes for an elegant and flavorful appetizer. The combination of tender steak, sweet onions, and a tangy sauce atop crunchy baguette slices is sure to impress your guests. Perfect for holidays or special occasions, this recipe can also be prepared ahead of time.

A close-up view of several small white bread rounds topped with three visible layers, arranged on a white plate with a golden rim placed on a white marbled texture. The bottom layer is a slice of toasted baguette, golden brown with a soft texture inside. The middle layer is a spread of creamy white mustard or sauce evenly covering the bread. The top layer is a thick slice of medium-rare beef steak, pink with a dark brown, slightly charred edge. On top of the steak slices, there is a chunky golden-brown onion relish, scattered with small green herb leaves. photo taken with an iphone --ar 4:5 --v 7

Ingredients

1 pound filet mignon or tenderloin
Salt and black pepper to taste

2 tablespoons unsalted butter (for steak)
1 teaspoon garlic powder

1 teaspoon dried thyme
Baguette, thinly sliced

Olive oil for brushing
1/2 cup mayonnaise
2 tablespoons horseradish

1 tablespoon Dijon mustard
1 tablespoon lemon juice
2 tablespoons unsalted butter (for shallots)

2 large shallots, thinly sliced
1 tablespoon balsamic vinegar
1 tablespoon brown sugar

Salt and black pepper to taste (for sauce and shallots)

Instructions

Step 1: Season the steak evenly with salt, black pepper, garlic powder, and dried thyme. Let it rest for at least 30 minutes to absorb the flavors.
Step 2: In a small bowl, combine mayonnaise, horseradish, Dijon mustard, and lemon juice. Season with salt and pepper, then refrigerate until ready to use.

Step 3: In a skillet over medium heat, melt butter and add the sliced shallots. Cook, stirring occasionally, until softened.
Step 4: Add balsamic vinegar, brown sugar, salt, and pepper to the shallots. Continue cooking for about 30 minutes until they are caramelized and golden brown. Remove from heat and set aside.
Step 5: Heat olive oil in a skillet over medium-high heat. Cook the steak to your preferred doneness (about 4 minutes per side for medium-rare), then remove from heat and let it rest.

Step 6: Preheat the oven to 375°F (190°C). Brush baguette slices with olive oil and arrange them on a baking sheet. Toast for 5-7 minutes until golden and crisp.
Step 7: Slice the rested steak into thin strips. Spread a layer of horseradish sauce on each toasted baguette slice, then top with steak slices and a spoonful of caramelized shallots.
Step 8: Arrange the crostini on a serving platter and garnish with fresh thyme or parsley if desired. Serve immediately.

Tips & Variations

Use a good quality baguette and slice it thinly for the best crunch and presentation.
If you prefer a milder sauce, reduce the horseradish or substitute with creamy ranch dressing.
Caramelize shallots slowly over low heat to develop deep, sweet flavors without burning.

Substitute filet mignon with sirloin or ribeye for a more budget-friendly option.
For extra freshness, add a sprinkle of chopped fresh parsley or thyme right before serving.

Storage

Store leftover horseradish sauce and caramelized shallots separately in airtight containers in the refrigerator for up to 3 days. Cooked steak can be stored wrapped tightly for up to 2 days. Assemble crostini just before serving to keep the baguette crisp. Reheat steak gently in a warm oven and toast baguette slices fresh to maintain texture.

How to Serve

The image shows a white plate with round bread slices as the base layer, each piece topped with a thin layer of light yellow mayo or sauce. On top of that, there is a thick slice of medium-rare steak with a pink center and a dark brown crust. The top layer consists of chunky, caramelized onions or a fruit chutney with a golden-brown color, scattered with small green herb pieces. The plate rests on a white marbled surface. photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I prepare the horseradish sauce and caramelized shallots ahead of time?

Yes, both the horseradish sauce and caramelized shallots can be made a day in advance and stored in the refrigerator. This helps deepen their flavors and saves time on the day you serve the crostini.

What is the best way to reheat the steak without drying it out?

Reheat steak slices gently in a low oven (about 250°F or 120°C) for a few minutes, or briefly in a skillet over low heat. Avoid high heat to keep the steak tender and juicy.