If you’re craving a crowd-pleasing appetizer that feels fancy without the fuss, this steak crostini with creamy horseradish sauce and sweet caramelized onions is your golden ticket. Each bite is buttery, bold, and totally unforgettable. Whether you’re hosting a holiday gathering or setting out date night snacks, these bite-sized beauties bring flavor and flair to the table fast.
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This Steak Crostini Is a Total Showstopper
Let’s talk flavor bombs. You’ve got crisp toasted baguette slices layered with juicy steak, a dreamy horseradish cream, and buttery balsamic shallots. It’s savory, sharp, sweet, and totally addictive. Best part? You can prep it all ahead and assemble just before serving. If you love party food that makes you look like a total kitchen genius without breaking a sweat, this one’s for you. Pair it with these juicy mini sandwiches for parties for the ultimate appetizer spread.
Ingredients You’ll Need
Here’s what you’ll need to whip up these steak crostini:
For the steak
filet mignon or sirloin
olive oil
salt and pepper
fresh rosemary or thyme (optional)
For the horseradish sauce
mayonnaise
prepared horseradish
Dijon mustard
lemon juice
garlic powder
salt
For the caramelized onions
shallots or yellow onions
unsalted butter
brown sugar
balsamic vinegar
pinch of salt
For the crostini base
1 French baguette
olive oil for brushing
flaky sea salt
To finish
fresh herbs like chives or parsley
cracked pepper
How to Make Steak Crostini with Horseradish and Onions
1. Prep and rest the steak
Rub steak with olive oil, salt, pepper, and herbs if using. Let it rest at room temperature for 20 to 30 minutes while you prep the other components.
2. Make the horseradish cream
Whisk mayo, horseradish, Dijon, lemon juice, garlic powder, and a pinch of salt. Taste and adjust the tang or heat as you like. Chill until ready to use.
3. Caramelize the onions
Slice onions thinly and sauté in butter over medium heat. After 10 minutes, sprinkle in the sugar and a splash of balsamic. Keep stirring until golden and jammy, about 25 minutes total.
4. Sear the steak
Heat a skillet or grill pan until smoking hot. Sear the steak on both sides until medium-rare, about 3 4 minutes per side. Let it rest for 10 minutes before slicing thin against the grain.
5. Make your crostini
Slice the baguette into thin rounds, brush with olive oil, sprinkle a bit of flaky salt, and bake at 375°F for 8 10 minutes until crisp and golden. For a sweet-and-savory twist, try serving these with brie, apple, and fig crostini too.
6. Assemble
Dollop a spoon of horseradish cream on each crostini, add a slice of steak, then top with caramelized onions. Finish with herbs and a crack of black pepper.
Make-Ahead & Storage Tips
Want less stress on party day? You can prep nearly every component ahead
Store the horseradish sauce and caramelized onions in the fridge for up to 48 hours
Sear your steak a few hours in advance and slice just before assembling
Toast the crostini the day before and store in an airtight container
Pro Tips for the Best Steak Crostini
Always rest the steak before slicing so the juices stay put
Use day-old baguette for perfect crostini texture
Slice the steak thin and against the grain for tenderness
Prep toppings before to keep things moving during assembly
Use high-quality olive oil it makes a big difference
Top with fresh herbs for color and that final flavor pop
If you’re going all out, serve alongside these crispy loaded Hasselback potato bites
Delicious Variations You Can Try
Swap horseradish with garlic aioli if you want less heat
Top with crumbled blue cheese or gorgonzola for an extra punch
Use whipped feta or goat cheese in place of horseradish cream
Make mini crostini with thinner bread slices for bite-sized apps
Grill the steak instead of pan searing for smoky vibes
FAQ You Asked, We Answered
Can I serve steak crostini cold or room temp?
You can, but warm steak is best. If serving room temp, bring the steak and onions to a mild warmth before assembling so the flavors shine.
What can I use instead of horseradish?
Try garlic aioli, whipped feta, or even a tangy yogurt spread. Anything creamy with a little zing works well here.
How do I keep crostini from getting soggy?
Assemble right before serving, or toast the bread extra crisp. You can also spread a tiny bit of butter or cheese between the bread and sauce to create a moisture barrier.
More Appetizer Recipes You’ll Love
Pair your steak crostini with these party favorites for a spread your guests will rave about
Try these juicy mini sandwiches for handheld goodness
Whip up some brie, apple, and fig crostini for a sweet-savory combo
And don’t miss crispy loaded Hasselback potato bites to round it all out
Follow us on Pinterest for more cozy ideas, or join the fun on Facebook
Steak Crostini with a Creamy Horseradish Sauce and Caramelized Onions
Ingredients
- FOR THE STEAK
- filet mignon or sirloin
- olive oil
- salt and pepper
- fresh rosemary or thyme optional
- FOR THE HORSERADISH SAUCE
- mayonnaise
- prepared horseradish
- Dijon mustard
- lemon juice
- garlic powder
- salt
- FOR THE CARAMELIZED ONIONS
- shallots or yellow onions
- unsalted butter
- brown sugar
- balsamic vinegar
- pinch of salt
- FOR THE CROSTINI BASE
- 1 French baguette
- olive oil for brushing
- flaky sea salt
- TO FINISH
- fresh herbs like chives or parsley
- cracked pepper
Instructions
- 1. Rub steak with olive oil, salt, pepper, and herbs if using. Let it rest at room temperature for 20 to 30 minutes while you prep the other components.
- 2. Whisk mayo, horseradish, Dijon, lemon juice, garlic powder, and a pinch of salt. Chill until ready to use.
- 3. Slice onions thinly and sauté in butter over medium heat. After 10 minutes, add brown sugar and balsamic vinegar. Cook until golden and jammy, about 25 minutes.
- 4. Heat a skillet or grill pan until very hot. Sear steak for 3 to 4 minutes per side for medium-rare. Let rest 10 minutes, then slice thinly against the grain.
- 5. Slice baguette into thin rounds, brush with olive oil, sprinkle salt, and bake at 375°F for 8 to 10 minutes until golden.
- 6. Top each crostini with horseradish cream, steak slice, caramelized onions, herbs, and cracked pepper.