These steak crostini with caramelised onions and chimichurri are the perfect appetiser to feed a crowd for the holidays or a special occasion. With tender, medium rare slices of steak on a bed of sweet, homemade caramelised onions, crunchy toasted baguette and a drizzle of fresh and vibrant chimichurri, these are basically just bite-sized steak sandwiches!
Crostini are the perfect appetiser for Christmas or New Years as they are elegant bites that can be made with literally anything and are so easy to assemble. This version is a nod to the classic steak sandwich but made just that little bit fancy.
Each element can be made ahead of time so you can simply toast your baguette slices and assemble when your guests arrive.
The key flavours of this bite-sized steak sandwich are the caramelised onions which take a little bit of time but are insanely good. Maybe make extra as I guarantee you’ll want to eat these on everything. This is then combined with perfectly cooked, medium rare steak drizzled with a quick and punchy chimichurri style sauce.
Is it bold to serve an appetiser that contains raw garlic to your guests? Probably, but the flavour is so very worth it!
If you’re looking for more appetiser recipes, make sure to also try these easy smoked salmon crostini or these seared scallops with avocado and smoked salmon which are my personal favourite!
Key Ingredients
There are a couple of elements to this recipe, but all use quite simple ingredients making it a very approachable recipe for when you want to make something a little special.
Note all ingredients and their quantities are laid out in the recipe card at the bottom of this post.
- Steak – you can use any cut of steak you prefer but you want something that is tender and ideal for quick cooking. I used a ribeye as it was a nice thick cut. Eye Fillet (filet mignon) or porterhouse (sirloin) are also tender cuts that work well for this recipe.
- Brown onions – also known as yellow onions, they are thinly sliced and then cooked down slowly for around 20-30 minutes with a little salt and oil until they are beautifully caramelised.
- Red wine vinegar – used to flavour the caramelised onions as well as being a key component in the chimichurri sauce.
- Brown sugar – helps to finish off the caramelised onions, adding that extra sweetness.
- Fresh parsley – essential for the chimichurri sauce. The Italian, flat leaf parsley works best.
- Garlic – gives the chimichurri that punchy, spicy flavour. Adjust the quantity based on your tastes and size of your cloves.
- French baguette – sliced and toasted to create the base of the crostini.
- Rocket leaves – also known as arugula, I like to use the smaller, baby leaves on the crostini to add a little peppery flavour and freshness. It also helps prevent the bread from becoming soggy!
Step-By-Step Instructions
There are a couple of elements that make up these steak crostini so it can be good to break them down and make some ahead of time so you’re not feeling rushed when it comes time to assemble.
This is my recommendation for order of operations;
- Start the caramelised onions
- Make the chimichurri
- Finish the caramelised onions
- Cook and rest the steak
- Slice and toast the baguette
- Assemble!
How to make caramelised onions
To make caramelised onions, start by peeling and slicing the onions. Cut each onion in half, then slice into thin, half-moon shapes. You want even slices that are thin but not overly so, as very thin slices may burn.
Add a little olive oil to a frying pan over medium-low heat, then add the onions. Begin sautéing, allowing the onions to soften. They’ll go from translucent to golden, gradually darkening. Make sure to stir them frequently with a wooden spoon to prevent sticking or burning.
After about 20 minutes, the onions should start caramelising naturally as they release their sweetness. Add the red wine vinegar to deglaze the pan, loosening any caramelised bits stuck to the bottom and sprinkle in the brown sugar.
Continue cooking for another 5–10 minutes until the onions are deep brown, sticky, and have a rich, sweet flavour. You can now set these aside until you’re ready to use them.
The next step is to make a quick chimichurri. Chimichurri is a fresh and vibrant sauce originating from Argentina that is usually served with grilled meats. It’s characterised by its tangy, herbaceous, garlicky flavour and it’s SO GOOD with a rare to medium rare steak.
My version uses a bunch of finely chopped fresh parsley combined with olive oil, red wine vinegar, fresh garlic, seasoned with a pinch of chilli flakes and salt and pepper. Once you have everything mixed up together you can set it aside as the flavours will infuse.
Now you’re ready to cook your steak. How you cook this will be personal preference but a little salt and pepper and oil in a pan until just medium rare is perfect. I don’t think these crostini are a place for a well done steak as we want to be able to bite them so the more tender the better.
Slice the baguette and brush the slices with some olive oil and toast under the grill until golden.
With all of your elements ready, you can now assemble the steak crostini! Start with your toasted baguette slice, add a few baby rocket leaves and then some of the caramelised onion. Top with a slice of steak and spoon over some of the chimichurri. Place the crostini on a serving plate and that’s it!
Recipe FAQs
Yes! Caramelised onions can be made up to 3 days in advance. Store them in an airtight container in the fridge, then reheat them if you like gently on the stovetop or in the microwave before assembling.
You can serve them either! Serving cold can be easier as you can make the elements ahead of time, but you can choose to serve with the onions and steak still warm which is delicious.
Yes, you can substitute the baguette with gluten-free bread or crackers to make this recipe gluten-free.
Tender cuts like porterhouse, ribeye, eye fillet, or sirloin are ideal for crostini. These cuts are flavourful, cook quickly, and slice easily, making them perfect for bite-sized servings.
If you do make this recipe, please be sure to leave a comment and ⭐⭐⭐⭐⭐ rating below! And tag any of your creations on Instagram with @eightforestlane as I would love to see.
More bite-sized snacks:
Easy Baked Beef Meatballs
Air Fryer Pork Belly Bites
Classic Sausage Rolls
Salt and Pepper Squid
Steak Crostini with Caramelised Onions and Chimichurri
Equipment
Ingredients
For the caramelised onions:
- 1 tablespoon olive oil
- 2 large brown onions thinly sliced
- Pinch salt
- 2 tablespoons red wine vinegar
- 1 tablespoon brown sugar
For the chimichurri:
- ½ cup fresh parsley chopped
- 2–3 cloves garlic finely diced or minced
- 2 tablespoons olive oil
- 2 tablespoons red wine vinegar
- Pinch of chilli flakes
- Salt and pepper to taste
For the steak crostini:
- 350–400 grams steak your choice of cut
- 2 tablespoons olive oil divided
- Salt and pepper
- 1 French baguette sliced into 1 cm rounds
- 1 cup baby rocket leaves
Instructions
- Make the caramelised onions. Heat 1 tablespoon of olive oil in a large pan over medium/low heat. Add the sliced onions and a pinch of salt. Cook, stirring occasionally, for 15–20 minutes until they soften and turn golden.
- Add the red wine vinegar and brown sugar, stirring to combine, and cook for another 5–10 minutes until the onions are caramelised and sticky.
- Make the chimichurri. In a small bowl, combine the chopped parsley, garlic, olive oil, red wine vinegar, and a pinch of chilli flakes. Stir well, then season with salt and pepper to taste. Set aside.
- Cook the steak. Season the steak with salt and pepper on both sides. Heat 1 tablespoon of olive oil in a pan over medium-high heat. When hot, add the steak and cook to your desired level of doneness (about 3–4 minutes per side for medium-rare, depending on thickness).
- Once cooked, remove the steak from the pan and let it rest for 5 minutes, then slice thinly against the grain.
- Prepare the crostini. Preheat your oven grill (broiler) to medium-high. Arrange the baguette slices on a baking tray, then brush each side lightly with the remaining olive oil.
- Place under the grill for 1–2 minutes per side, or until the bread is golden and crisp.
- Assemble the crostini. Place a few baby rocket leaves on each baguette slice and top with a spoonful of caramelised onions, then add a slice of steak. Finish with a drizzle of the chimichurri and serve immediately.
Notes
Nutrition
Nutritional information is provided as a guide only and is calculated using automated online tools, therefore we cannot guarantee the accuracy. We encourage you to make your own calculations based on the actual ingredients used in your recipe.
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