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Home » Blog » Appetizer

Caramelized Onion Brie Crostini

Published: January 31, 2023 · Last Updated: February 17, 2023 by Rhonda

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For a delicious appetizer, top these caramelized onion crostini with a slice of brie. Makes a perfect bite for entertaining!

Melted brie and caramelized onions on top of crostini.

This crostini reminds me of my favorite parts of French onion soup - the sweet onions, crispy bread and melted cheese on top.

Jump to:
  • Basic Steps
  • Cheese
  • Make Ahead and Time Saver Tips
  • Are Crostini and Bruschetta the Same Thing?
  • Saving Leftovers
  • Some Common FAQ's
  • Other Favorite Crostini and Bruschetta Recipes
  • Caramelized Onion Brie Crostini

Basic Steps

Baguette, brie cheese, onions, butter, salt, pepper and oil on a table.
  • Caramelize Onions. We love to keep caramelized onions in the fridge and freezer which then makes this recipe ready in just minutes and perfect for unexpected guests.
  • Make Crostini. Use a fresh, thinly sliced baguette, drizzle with olive oil, and bake.
  • Slice Cheese. We use a double or triple cream brie round. Both a brie round or wedges will work in this recipe.
  • Assemble. Add caramelized onions and sliced brie to each crostini.
  • Broil. Brie should be soft and melted.
  • Garnish. This is optional, but we love a little chopped parsley sprinkled over the top.
  • Serve.

Cheese

There is just something delicious and mouth watering about a creamy, melted brie cheese. It goes perfect with the caramelized onions and crunchy crostini. Not a brie fan? Substitute swiss cheese or gruyere cheese for the brie and bake just until the cheese begins to melt.

It is perfectly safe to eat the rind on brie cheese. We found, in this recipe, a thinner rind on the brie helps it melt a little easier. To thin the rind, gently run a sharp knife over the rind. After thinning the rind, cut the brie into slices about ¼ inch thick.

Brie round with rind and with rind scraped off.

Make Ahead and Time Saver Tips

  • Make crostini up to a day in advance and store on the counter in an airtight container. You can also purchase, pre-made, crostini from most grocery stores to save a little time. See Homemade Crostini for more notes and detailed instructions. 
  • Caramelized onions take about an hour to do right and shouldn't be rushed. We make ours in large batches and keep some in the fridge and freezer to add to recipes.
    See How to Caramelize Onions for more notes and detailed instructions. 
  • Assemble the crostini earlier in the day (up to 6 hours in advance) and store in the fridge. Remove and bake as needed.
Caramelized onions in a dish.

Are Crostini and Bruschetta the Same Thing?

The terms crostini and bruschetta have come to be used interchangeably but technically they are not the same. Crostini are usually made from a smaller diameter loaf of bread with a less rustic feel - think a more even texture, like a baguette. Bruschetta are made from a larger, thicker slice of bread that has a more rustic texture - think lots of nice air holes or sourdough! Both are toasted or grilled. You can use bruschetta for crostini recipes and crostini for bruschetta recipes. You may need to increase or decrease the amount of toppings depending on which you make.

Saving Leftovers

The FDA recommends discarding any perishable food that has been out at room temperature for more than 2 hours.

We don't recommend saving pre-made crostini. The crostini usually becomes soft and soggy from the toppings.

Layering caramelized onions and brie slices on crostini.

Some Common FAQ's

Do I have to remove the rind on the brie cheese?

NO! It is perfectly safe to eat the rind. We found, in this recipe, the brie melts a little easier if the rind on the brie is thinned a little. This is done by gently running a sharp knife over the rind and takes just a few seconds.

What is the key to caramelizing onions?

Time! This process can't be rushed if you want that amazing caramelized finish to the onions. It takes about an hour. We keep caramelized onions in our freezer to use as needed in recipes. See How To Caramelize Onions for more notes and detailed instructions. 

Can I serve this on plain sliced baguettes instead of crostini?

The crunch of the crostini is a big element in this appetizer, but it can be served on a plain slice of baguette. For more notes and make ahead tips see Homemade Crostini.

Crostini with melted brie and caramelized onion

Other Favorite Crostini and Bruschetta Recipes

  • Pear and Goat Cheese Crostini
  • Strawberry Goat Cheese Crostini
  • Homemade Crostini
  • Grilled Tomato Crostini
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Caramelized onions and melted brie on a crostini.

Caramelized Onion Brie Crostini


  • Author: Rhonda
  • Total Time: 1 hour 15 minutes
  • Yield: 24 pieces 1x
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Description

This caramelized onion and brie crostini is a delicious appetizer perfect for entertaining!


Ingredients

Scale
  • 2 large onions
  • 2 Tablespoons butter
  • 4 ounces brie 
  • 1 baguette sliced 
  • 2 Tablespoons olive oil
  • chopped parsley for garnish (OPTIONAL)

Instructions

Make Caramelized Onions

  1. Peel and thinly slice the onions.
  2. Add onions and butter to a cast iron skillet over medium heat. Cook, stirring frequently until onions are caramelized. Caramelizing onions takes about an hour - make these in advance and keep on hand for using in recipes. 

Make Crostini

  1. Spread the baguette slices in a single layer on a lined baking sheet pan. Drizzle, spray, or brush with olive oil. Bake at 375°F for 5-10 minutes or until lightly browned. 
  2. Remove once done and set aside until ready to assemble.

Prepare Brie

  1. Using a sharp knife scrape over the rind on the top and bottom of the brie. This will remove some of the rind making the brie melt a little easier on the crostini. It is absolutely fine to eat the rind on the brie, but for this recipe we find it melts a little easier if it is thinned out. 
  2. Slice the brie into slices about ¼ inch thick.

Assemble Crostini 

  1. Place crostini on a baking sheet pan. 
  2. Top each crostini with 1-2 teaspoons caramelized onions.
  3. Place a slice of brie on top of the onions.
  4. Broil for 2-3 minutes until the cheese is melted.
  5. Remove from oven. Garnish with chopped parsley (OPTIONAL). Serve warm.

Notes

Make Ahead of Time. These crostini take just minutes to assemble if the caramelized onions and crostini are already done making this a great recipe for unexpected guests. Ready in just minutes, easy to assemble, and delicious!

Cheese. If you aren't a fan of brie substitute swiss or gruyere cheese. Leave the rind on the brie or thin it out by gently running a sharp knife over it before slicing.

Caramelized Onions. Make these in large batches and keep in the refrigerator or freezer to use in dishes. See How to Caramelize Onions for more notes and detailed instructions. 

Crostini. Make the crostini up to a day ahead of time and store in an airtight container on the counter. See Homemade Crostini for more notes and detailed instructions. 

  • Prep Time: 5 minutes
  • Cook Time: 1 hour 10 minutes
  • Category: crostini
  • Method: Baking
  • Cuisine: American

Nutrition

  • Serving Size: 1 piece
  • Calories: 31
  • Sugar: 0.3 g
  • Sodium: 30.7 mg
  • Fat: 2.8 g
  • Carbohydrates: 0.6 g
  • Protein: 1 g
  • Cholesterol: 5.3 mg

Keywords: appetizer, cheese, entertaining

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