It’s like picking up a piece of French onion soup with your hands! Caramelized Onion Crostini Appetizers are topped with caramelized onions and Gruyere cheese for an indulgent appetizer.
Who doesn’t love French onion soup. I’ve got a fantastic way to get all that rich flavor without needing a spoon. Caramelized Onion Crostini Appetizers are everything you love about French onion soup without the mess.
Sweet caramelized onions and gruyere on top French bread are a perfect two bite appetizer that will WOW your guests. Delicious right out of the oven, but also scrumptious at room temperature.
The crostini base is sturdy enough to hold the onions and cheese without making a gooey mess. If you love French appetizers, then try some mini croque monsieurs along side these.
Cognac added to the caramelized onions add a depth of flavor that you wont’ get with just beef broth. Cognac is a specific type of Brandy that is made in a special region of France.
Why you’ll love crostini appetizers
- They’re great for guests before dinner or as an appetizer for Game Day.
- You won’t feel guilty about enjoying several of these delicious crostinis as they’re only 2-3 bites each.
- There’s no mess – everything fits under the melted cheese on the slice of baguette.
- Caramelized onions can be made in advance.
What you’ll need
- Onions – Vidalia or yellow will work for this recipe, Vidalias are naturally sweeter so they caramelize easily but any type of onion will be delicious once caramelized.
- Gruyere – this firm, yellow Swiss cheese is delicious and melts great.
- Cognac – you can use any type of brandy.
- Baguette – crostini means “little toasts” so the baguette is delicious in that it holds the wet ingredients without falling apart in your hand.
- Beef Broth – if you want to make it vegetarian, use vegetable broth instead.
- Pantry staples – olive oil, butter, sugar, salt, pepper
Pro tip: You may think these would be difficult to make for a party, but you can do everything in advance and just put them in the oven before you’re ready to serve. Prep them up to two days in advance.
How to make caramelized onion crostini appetizers
To get started, all you have to do is caramelize the onions. Not to worry, it’s really easy.
It’s going to take 30 minutes no matter what you do, you really can’t speed that up. In order for sweetness to come through, you have to let them cook slowly. So be patient.
Add a little butter and olive oil to a skillet with a lid and once it’s hot, add the onions and cover, cooking over low heat for 15 minutes.
Remove the lid, add some salt and sugar and cook for an additional 15 minutes, stirring occasionally. You can also just cook them on low for 30 minutes.
At the end you’ll add Cognac and beef broth. You can easily substitute vegetable broth but don’t leave out the Cognac. That’s what gives it the depth of flavors that you love in French onion soup.
Once the onions are nice and golden brown, just assemble your crostini adding lots of gruyere to the top and bake.
Bake for 15 minutes or until the cheese has started to brown.
You’ll love the rich flavor you get in this easy to make appetizer. If you don’t use all the onions, they are great added to a quiche or rolls.
FAQs and tips
I selected medium sized onions. Don’t worry if you have extra onions, they are so delicious, you’ll be adding them to eggs, or on top of a burger or on a grilled cheese.
If you have a mandolin kitchen slicer, you can slice the onions nice and thin and then cut them in half, so they are half moon shaped. Otherwise, just slice them as thin as your knife skills allow.
You can prepare caramelized onions two to five days in advance and keep it in the refrigerator.
Yes, just substitute vegetable broth for the beef broth.
Check out these appetizers for your next party
Caramelized Onion Crostini Appetizer
- 1 tablespoon olive oil
- 2 tablespoons butter
- 4 ½ cups yellow onions about 3–4 onions
- ½ teaspoon salt
- pinch sugar
- 2 tablespoons cognac
- 1 cup beef broth
- baguette sliced inot ½ inch slices
- 8 ounces gruyere 2 cups
- Add butter and olive oil to a large skillet with a lid and cook over medium heat. Toss onions and cover for 15 minutes. Remove the lid, stir in salt and sugar and cook an additional 15 minutes until golden brown. Pour in cognac and beef broth and turn heat up. Simmer until it has reduced, about 15 minutes. Adjust salt if needed and add pepper.
- Preheat oven to 375º. Line a baking sheet with Parchment paper.
- Add a large spoonful of onions onto each bread slice and top with cheese. Bake for 15 minutes or until the cheese has started to brown.
Barbara’s Tips + Notes
- You can make the onions in advance and refrigerate until needed.
- You can use any type of brandy.
- If making vegetarian, substitute vegetable broth for beef broth.
- Assemble these a day in advance and then bake before serving.
- They taste best warm but are still delicious at room temperature.
Would give these a 4.8. Just finished eating these. Heavenly. Added some fresh time and plenty of salt and fresh cracked pepper.
Barbara Curry says
Anything with caramelized onions has to be good!