Name: Caramelized Onion and Blue Cheese Crostini Recipe
Prep time: 15 min
Cook time: 1 h 15 min
Total time: 1 h 30 min
Cuisine: American
Ingredients: 1 large vidalia onion (about 12 oz), peeled, halved, and thinly sliced; 2 tablespoons extra-virgin olive oil; ¼ teaspoon kosher salt; 2 teaspoons balsamic vinegar; 1 baguette, sliced into ¼-inch rounds; ⅓ cup fig preserves; ¼ cup blue cheese crumbles; 2 sprigs fresh rosemary, torn or roughly chopped; freshly ground black pepper, for serving

Jump to Recipe· 4.7 from 57 reviews

If you’ve ever been craving a sophisticated yet surprisingly easy appetizer that’ll wow a crowd, you’re going to love this Caramelized Onion and Blue Cheese Crostini Recipe. It combines sweet, savory, and tangy flavors in such a perfect balance. Trust me, once you try it, you’ll want to make it for every party, dinner, or cozy night in. Stick around because I’m sharing all my tips to help you get those onions just right and make your crostini shine!

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Why This Recipe Works

Perfect Flavor Balance: The sweetness of the caramelized onions and fig jam pairs beautifully with the tangy, creamy blue cheese.
Simple Ingredients, Big Impact: It uses pantry staples and a few quality ingredients to create something special without complication.
Crowd Pleaser: These crostini are easy to make ahead and serve, making your hosting stress-free and impressive.
Textural Contrast: Crunchy toasted baguette against silky onions and crumbly cheese keeps every bite exciting.

Caramelized Onion and Blue Cheese Crostini, flavorful appetizer with caramelized onions, easy blue cheese crostini, elegant party hors d'oeuvres, savory finger food - There is a white baking tray with twelve toasted slices of bread arranged in three rows of four. Each slice has a layer of dark caramelized onions topped with crumbled creamy blue cheese that is white with blue veins. To the right of the tray, there are some plain slices of bread showing a soft, light inside. Above the tray, a black cast iron pan holds more caramelized onions with a silver fork resting inside. On the left side, a wedge of blue cheese and sprigs of fresh herbs sit on the white marbled surface. Below this, a small white bowl contains more blue cheese crumbles, next to a glass jar of dark honey with a spoon inside. Photo taken with an iphone --ar 2:3 --v 7

Ingredients & Why They Work

This Caramelized Onion and Blue Cheese Crostini Recipe relies on ingredients that complement each other like old friends — the sweetness of Vidalia onions and fig preserves brightens the richness of blue cheese, while a crisp toasted baguette holds it all together. Choosing fresh ingredients really elevates the final bite, so I recommend looking for a good quality baguette and creamy, flavorful blue cheese.

Vidalia onion: Sweet onions caramelize beautifully, becoming soft and jammy without bitterness.
Extra-virgin olive oil: Adds richness and helps the onions cook gently without sticking.
Kosher salt: Seasoning early helps draw out moisture from the onions and enhances their natural sweetness.
Balsamic vinegar: Adds a subtle tang and depth to the caramelized onions at the end of cooking.
Baguette: Slice thin for perfect bite-sized crostini that crisp up nicely in the oven.
Fig preserves: Sweet jammy flavor acts as the perfect base on each crostini before topping.
Blue cheese crumbles: The creamy, salty tang cuts through the sweetness with flair.
Fresh rosemary: Adds an herbal note for aroma and a pop of color.
Freshly ground black pepper: A final seasoning touch that brightens the whole thing.

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Note: You’ll find the complete list of ingredients, along with their exact measurements, in the printable recipe card at the bottom of this post.

Make It Your Way

I love to tweak this Caramelized Onion and Blue Cheese Crostini Recipe depending on the occasion. Sometimes I swap fig preserves for apricot jam for a slightly tangier sweetness, or sprinkle crushed walnuts on top for crunch. Feel free to customize with ingredients you love — this recipe is forgiving and adaptable!

Variation: When I hosted a wine tasting, I swapped rosemary for thyme and it paired beautifully with a bold red wine—try different herbs to suit your menu.
Dietary tweaks: For a vegetarian version, just be sure your blue cheese doesn’t contain animal rennet, or try a creamy goat cheese instead.
Seasonal tweaks: Add a drizzle of honey and some toasted pecans in the fall for a cozy twist I absolutely adored last year.

Step-by-Step: How I Make Caramelized Onion and Blue Cheese Crostini Recipe

Step 1: Slow-Caramelize the Onions for Maximum Sweetness

Start by heating your extra-virgin olive oil in a heavy-bottomed skillet over medium-high heat. Add your thinly sliced Vidalia onions and sprinkle with kosher salt to help release their natural moisture. Stir the onions for about 5 minutes until they begin softening but aren’t browning unevenly. Now, lower the heat to medium-low and pop a lid on the pan. This slow cooking method for about an hour, with a stir every 10-15 minutes, is the secret to those deep, jammy onions. If you see the onions sticking or burning, add a splash of water or broth to loosen the fond—this keeps the flavor building and stops the cooking process from going haywire. When the onions are almost ready, stir in the balsamic vinegar for brightness, and then remove them from the heat.

Step 2: Prepare and Toast the Baguette Slices

While your onions work their magic, preheat your oven to 400°F (204°C). Slice your baguette into thin, quarter-inch rounds, which is perfect for finger food. Lay them out evenly on a baking sheet lined with parchment paper or foil to keep cleanup easy. You’ll toast these rounds after topping them, but it’s a good idea to watch them closely once they go in the oven to prevent burning.

Step 3: Assemble the Crostini and Finish in the Oven

Spread a small dollop (about 1-2 teaspoons) of fig preserves on each baguette slice. This sweet base pairs wonderfully with both the caramelized onions and blue cheese. Next, pile on a spoonful of those luscious caramelized onions followed by a chunk or crumble of blue cheese. Pop them back in the oven for 4-5 minutes so the cheese softens just a bit and the bread crisps perfectly. Once out, sprinkle with torn fresh rosemary and a few twists of black pepper. Now, get ready for your guests to ask for the recipe!

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Tips from My Kitchen

Patience is Key: Don’t rush caramelizing the onions—it takes time but the payoff is incredible sweetness and texture.
Even Slices: Using a serrated knife to slice your baguette helps prevent squashing the bread and ensures even toasting.
Don’t Overcrowd: Give your crostini space on the pan so they toast evenly instead of steaming.
Watch the Cheese: Blue cheese can melt quickly—remove the crostini as soon as it looks soft and bubbly to avoid overpowering the texture.

How to Serve Caramelized Onion and Blue Cheese Crostini Recipe

Garnishes

I always use fresh rosemary because it adds such an amazing aroma and a pop of herbal earthiness that balances the richness. A quick sprinkle of freshly ground black pepper at the end brightens all the flavors and adds just the right hint of heat without overpowering.

Side Dishes

These crostini pair wonderfully with a fresh green salad tossed in a light vinaigrette or a bowl of marinated olives. For an easy yet elegant spread, I like to serve alongside charcuterie boards featuring prosciutto, figs, and nuts — the flavor profiles just sing together.

Creative Ways to Present

For special occasions, I’ve served these crostini on a large wooden board lined with fresh herbs and edible flowers—so pretty and inviting. I’ve also layered them on tiered trays to make them the centerpiece of an appetizer buffet. It’s always a hit, and people love the finger food vibe.

Make Ahead and Storage

Storing Leftovers

If you happen to have leftovers — though I doubt it! — I recommend storing the caramelized onions separately in an airtight container in the fridge for up to four days. Toasted baguette slices keep best in a sealed bag at room temperature to maintain crunch.

Freezing

I’ve frozen caramelized onions by themselves successfully; just thaw them slowly in the fridge and reheat gently. Baguette slices can also be frozen before toasting and toasted straight from the freezer later. However, I don’t recommend freezing assembled crostini as blue cheese texture can change and bread gets soggy.

Reheating

To reheat, warm the caramelized onions gently in a skillet or microwave until heated through. Toast baguette slices in the oven for a few minutes to refresh crispiness. Then assemble fresh with blue cheese and toppings right before serving to keep the best texture and flavor.

FAQs

Can I use other types of onions for this recipe?

Absolutely! While Vidalia onions are sweet and ideal for caramelizing, yellow or white onions work too. Just note that they might have a slightly stronger flavor and may need a bit more cooking time to develop sweetness.
How do I know when caramelized onions are done?

They should be soft, deep golden brown, and have a jammy texture. You’ll smell a rich, sweet aroma and see that the onions have significantly reduced in volume.
Can I prepare this recipe vegan or dairy-free?

Yes! Simply replace blue cheese with a vegan cheese alternative or a creamy nut-based spread. The rest of the recipe is naturally vegan-friendly.
What’s the best way to store leftover crostini?

Store components separately—onions in an airtight container in the refrigerator and toasted bread at room temperature. Assemble just before serving again for the best taste and texture.

Final Thoughts

This Caramelized Onion and Blue Cheese Crostini Recipe is one of those dishes that feels fancy but comes together without fuss, making it my go-to for everything from casual get-togethers to holiday parties. The first time I made it, friends raved for days, which was such a confidence boost! I’m confident you’ll enjoy the blend of sweet, savory, and tangy flavors that dance on your palate. So grab those onions, your favorite baguette, and let’s get to cooking — I promise, this recipe will become a classic in your kitchen, too.

Caramelized Onion and Blue Cheese Crostini Recipe