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    Home » Vegetarian

    French Onion Crostini

    Published: Nov 4, 2023 by Stacey

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    Jump to Recipe·Print Recipe·5 from 1 review
    side view of crunchy french onion soup crostini on a serving tray

    French onion soup. I remember loving it starting in my teen years. But I absolutely became obsessed when I had the best French onion soup of my life at Pot au Feu in Providence, RI. This was in college and all these years later, even now as I am writing this, I want to jump in my car and go to Providence just to have this soup. So let's make French onion crostini - an easy appetizer that tastes like the bread that floats on top of that amazing soup.

    The Top is the Best Part of the Soup! Right?

    My favorite part about French onion soup is the awesome slice of bread on top. It has cheese, it's toasty and it's soaking in soup beneath. Well, imagine just eating the bread part? Yeah, so that's what this crostini is. The crown jewel of French onion soup.

    If you are a regular reader of my website, you know that I made a French onion grilled cheese with bacon a while back. Same concept as that: the incredible flavor of onions with a little port wine, except this is a bite-sized treat which will become your new favorite appetizer.

    For the bread: you can use the bagged ciabatta sticks like I did with my canned crab toasties. Or you can opt for a thin French baguette and slice into ½" rounds. With this recipe, I took the slightly lazy way out and purchased already-sliced french bread rounds that were perfect for this! Bonus, you can freeze the bread you don't use and keep them for your next gathering. You can see two of the bread options in my video.

    close up view of one french onion crostini on a serving platter

    How to Make French Onion Crostini

    You need only a handful of ingredients to make this crowd-pleasing appetizer: sliced bread, onions, port wine, gruyere cheese, dried or fresh thyme, and a few other ingredients you already have on hand.

    • Slice your onions and start cooking them. Stir while you do other prep.
    • Chop the fresh thyme or used dried.
    • Shred the gruyere cheese.
    • Brush olive oil on bread.
    • Add the cooked onions and cheese to the bread.
    • Bake in oven for 10-15 minutes.
    • Serve immediately.
    overhead view of cooking the onions at the beginning of the process
    Onions at the beginning of cooking
    overhead view of what the onions should look like at the end of cooking
    Onions at the end of cooking
    Distribute onions on bread slices
    adding a pinch of gruyere cheese to the tops of french onion crostini
    Add a pinch of shredded gruyere to the top
    french onion crostini on a sheet pan ready to cook in the oven
    Bake in the oven for 10-15 minutes
    french onion soup crostini on a sheet pan right out of the oven
    Right out of the oven and ready for the platter

    Bread, Onions and Cheese Keeps it Real Simple

    This easy appetizer is perfect for entertaining and with the holidays around the corner, I know you're looking for a few quick wins to make hosting easier. Not only does this appetizer have very few ingredients, it's make-ahead friendly.

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    You can prepare the crostini a few hours ahead or even the day before and keep them in your fridge on a sheet pan. Take them out 20 minutes before popping in the oven and you're good to go.

    How to Freeze this Crostini & Reheat

    With this one, you can freeze it and reheat later. When I was testing this recipe I cooked a batch and froze them in packs of four.

    • Wrap the desired number of crostini in plastic wrap. Four works well. And I did double wrap them.
    • Take the wrapped crostini and place in a freezer-safe slider bag (quart-sized bags are awesome for this).
    • Take out of freezer when you want to reheat. I've let them defrost overnight in the fridge AND I've also taken out of the freezer and put directly into the toaster oven. Either way works!
    • Heat toaster oven to 325 degrees and let them cook until warm and toasty. If you think they might burn (toaster ovens are all different), tent a small piece of foil and place on top. Should be ready in 7-10 minutes.

    Cooking at Home for the Holidays

    It is late fall which means it's almost Thanksgiving, Hanukkah, Christmas, New Year's Eve and Super Bowl Sunday. It all happens so fast once Thanksgiving arrives, right? Holidays mean food - lots and lots of food. Maybe you're a seasoned home chef or maybe you're a beginner. Either way, there really has never been a better time to cook at home.

    I have a lot of great recipes right here with step-by-step written instructions as well as accompanying videos to walk you through the whole cooking process. I love cooking at home and I love making delicious food for all my loved ones. And if you're here - you probably do too. Thanks for stopping by and I hope you give this one a try. 🙂

    Looking for More Appetizers? I Gotcha Covered:

    • Shrimp & Gorgonzola Crostini
    • Brown Sugar Bacon Sticks w/Maple Syrup
    • Stuffed Mushrooms
    • Nana's Weird Hot Dog Appetizer
    • Phyllo Cups FIVE Ways
    • Honey, Butter Bourbon Shrimp
    • Crispy Thai Pork Toast

    Print
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    french onion crostini on a platter with thyme and craisin garnish

    French Onion Crostini


    5 Stars 4 Stars 3 Stars 2 Stars 1 Star

    5 from 1 review

    • Author: Stacey
    • Prep Time: 35 minutes
    • Cook Time: 15 minutes
    • Total Time: 50 minutes
    • Yield: 20 crostini 1x
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    Description

    Looking for a super easy, gourmet appetizer? Then you should definitely try my French onion crostini. Total winner.


    Ingredients

    Scale

    For cooking the onions:

    • 2 medium/large Vidalia onions, sliced
    • 2 tablespoons olive oil
    • ½ teaspoon salt
    • ¼ teaspoon pepper
    • ½ teaspoon fresh or dried thyme, plus extra for garnish
    • 3 tablespoons port wine
    • ½ tablespoon of sugar, optional

     

    • 20 small bread rounds (see note#1 about bread choices)
    • Olive oil for brushing on bread
    • 2 cups shredded gruyere cheese (one 4.9-ounce package)

     

    Optional garnish:

    • Fresh chopped parsley
    • Dried or fresh thyme

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    Instructions

    1. Cut two peeled onions in half and slice into thin strips (my video shows this well).

    2. Put sliced onions in a pan with olive oil, salt and pepper. Turn on medium-to-high heat for the first two minutes and stir onions to coat in olive oil. Turn heat down to low-to-medium. Stir off and on for about 20-30 minutes until onions are golden brown. Add the thyme half way through and stir. Towards the end of cooking add the sugar if you are using and stir a couple of minutes. Then add the port wine and stir. The wine will cook off. This means the liquid will soak into the onions and remaining liquid will evaporate. Onions are done when then are a dark golden brown as seen in the video. 
    3. While the onions are cooking, chop the fresh thyme if using. Gently pull the leaves from the stems and chop down into fine bits. Chop enough to add to the onions, plus a little extra for garnish.
    4.  Shred the gruyere cheese and set aside. I usually slice the hardened end off first before shredding.
    5.  Prepare the bread. If you are slicing the bread yourself, your bread rounds should be about ½” in thickness. I used already-sliced French bread and got 20 crostini’s out of it. If you are using a smaller bread like the ciabatta sticks, you will get a few more out of it. My video shows both bread options so you can see the sizes.
    6.  Pour some olive oil in a ramekin (a few tablespoons, more if needed). Brush a little olive oil on top of the bread with a pastry brush.
    7.  Once the onions are cooked and cooled a few minutes, use a fork to distribute to each slice of bread. You’ll need to eyeball-it to distribute evenly.
    8.  Take a pinch of gruyere cheese and place on top of the onions on each slice of bread.
    9.  Bake in a pre-heated oven at 400 for about 10-15 minutes until the cheese is melted and the edges are golden brown and crispy.
    10.  For presentation, place crostini on a small platter or plate. Sprinkle fresh parsley, if using, and some of the extra fresh thyme (or dried if you’re using that). Decorate with a few fresh thyme sprigs and craisins if you have on hand. Serve immediately.
    11.  These freeze well too. Just wrap in plastic wrap and place in freezer-safe slider bag. Reheat in toaster oven at 325 degrees when you’re craving a snack.

    Equipment

    Image of Calphalon Saute Pan with Lid (5QT)

    Calphalon Saute Pan with Lid (5QT)

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    Eco Smart Cutting Board

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    Folding Cheese Grater

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    Silicone Spatula Set

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    Image of Small Sheet Pan

    Small Sheet Pan

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    Notes

    1. See the video for visual on the bread options. You could use ciabatta sticks, like I used for my canned crab toasties. Another option is pre-sliced bread in a bag (use some for this recipe and save the rest for other occasions). Buy a thin French baguette at the store and slice the bread yourself (should be about ½” in thickness or just slightly less.) Remember, at the grocery store bakery there are often two types of French bread baguette. The thicker, fluffier loaf or the smaller, thin loaf. For crostini, you’ll want the thinner loaf.

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    1. Deb P

      February 14, 2026 at 5:52 pm

      Delicious! Great app for those who love French onion soup!

      Reply
      • Stacey

        February 20, 2026 at 2:34 pm

        Hey Deb - thanks so much! 🙂

        Reply

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