These caramelized onion brie crostini are a match made in appetizer heaven. They're incredible simple to prep yet feel uber elegant on the table. What's better than a garlic crostini topped with creamy brie, a spoonful of sweet, caramelized onions, and a sprig of fresh thyme? Nothing.
These crostini are truly the perfect appetizer for any holiday gathering and are sure to impress without any extra effort. Three ingredients, with the bulk of the work used for caramelizing the onions, but lemme tell you, they are SO worth it.
TL; DR Recipe Summary
- ⏱️ Cook Time: 1 hour for the onions
- 👩🏼🍳 Cook Level: Intermediate (solely for caramelizing the onions)
- 😋 Taste: Creamy, sweet, tangy, herby, garlicky, crunchy
- 🍽️ Best Served With: This is a fabulous recipe to serve with sweet potato rounds and ricotta, fresh baked spinach artichoke dip, cheesy pesto pizza pinwheels, and you can never go wrong with briny tomato sardine toasts.
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Trusted Tips and Reminders
- Do NOT add the flour to the onions! I took the ingredient photo anticipating using the flour, and in my first test, the onions with the flour ruined the flavor of the dish. So, ignore the flour in the photo.
- Take your time with caramelizing the onions low and slow. You can stir occasionally so that the onions do not burn, so be sure to give yourself the full hour to let the onions cook down.
- Take the brie out of the fridge 15-20 minutes before you want to use it so that it softens up prior to adding to the crostini.
The Main Ingredients
- Crostini - AKA crispy, toasted slices of bread. The ones I used are store-bought but you can also make your own. These are the vessels for the brie and onions on top.
- Onion - I like using a yellow or sweet onion to caramelize, and they add a gentle sweetness to the overall appetizer. Plus, who doesn't love the smell of simmering onions on the stove?
- Brie - Brie cheese is a moldy, relatively mild cheese that pairs really well with the onions and adds complexity when eaten together.
- Fresh Thyme - The herby flavor of thyme is a nice contrast to the sweet, rendered down onions and creamy brie. It's also my go to herb in most of my recipes.
Be sure to check out the recipe card at the end of this post for more information about quantities, measurements, and specific cooking instructions.
Simple Swaps and Substitutions
- If you are not team brie cheese, you can use a soft goat cheese or a slice of fresh mozzarella cheese.
- I've never used shallots to caramelize instead of traditional onions, but I can't imagine it being bad.
- Crostini can be made on your own by toasting up a sliced baguette until crispy.
- You can top with other herbs like rosemary or torn basil instead of thyme.
How to make caramelized onion brie crostini
Step 1: Peel and slice two medium sized onions and add to a medium bowl.
Step 2: Over a medium flame, melt butter then add in the sliced onions.
Step 3: Continue to let the onions sweet and cook down over a medium to medium low heat, stirring occasionally as to keep the onions from burning and sticking. The onions should have a sweet smell and be golden in color.
Step 4: Once the onions are done cooking, take off the heat. Take a small slice of brie and spread it onto the crostini, then add a small scoop of onions. Top with thyme and serve.
Brie and Onion Crostini FAQs
LOW AND SLOW! You don't want to rush the process, and a higher heat will certainly cook the onions, and will burn them. Keep the flame low, cook them slow, it will likely take you anywhere from 35 minutes to about an hour. It's worth it!
You can add caramelized onions to soup to make homemade french onion soup, or throw them into a sandwich like slow cooker pot roast sliders. You can also top them over crispy chicken cutlets and melt cheese on top for a "french onion chicken cutlet" option.
You can store them assembled as is if you are going to eat them shortly after storage, or you can add to the fridge for up to 3 days. If you want to simply save the leftover onions, add to an airtight container and add to the fridge for up to 5 days.
Try out some of my other appetizer recipes
Did you love this recipe? ⭐️⭐️⭐️⭐️⭐️ If you're just as in love with this recipe as I am, please share a comment below and rate it! Better yet, share this recipe with family and friends!! Thank you!
Caramelized Onion Brie Crostini
Equipment
- dutch oven
Ingredients
- 12 pieces Crostini
- 1 small Brie Cheese
- 2 medium Onions sliced
- 1 oz Fresh Thyme Sprigs
Instructions
- Peel and slice two medium sized onions and add to a medium bowl.
- Over a medium flame, melt butter then add in the sliced onions.
- Continue to let the onions sweet and cook down over a mediumt o medium low heat, stirring occasionally as to keep the onions from burning and sticking. The onions should have a sweet smell and be golden in color.
- Once the onions are done cooking, take off the heat. Take a small slice of brie and spread it onto the crostini, then add a small scoop of onions. Top with thyme and serve.
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