French Onion Crostini

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French Onion Crostini made with sweet caramelized onions, salty Gruyère cheese and fresh thyme piled on crusty bread. A party perfect appetizer!

When it comes to party appetizers, crostini is always a great option. They are bite-sized. They are easy to make and there are totally limitless options for how to top them. This version was inspired by my recent tutorial: How to Make Caramelized Onions . I have been wanting to put them on everything.

I had some Gruyere in the fridge, a baguette in the pantry and voilà: French Onion Crostini was born.

This is the perfect appetizer for your next game day, holiday gathering or dinner party. Caramelizing the onions takes a bit of time but you can do that ahead of time and assemble just before serving. You’re going to love these bites!

Let’s talk about what you will need to make them.

French Onion Crostini Ingredients:

All of the big flavors that you get from French Onion soup, you’ll find right here in these French Onion Crostini. And it’s only a handful of ingredients.

• ONIONS: To make one batch of crostini you’ll need 1 large yellow onion.
• BUTTER/OLIVE OIL: To caramelize the onions.
• SALT AND PEPPER
• FRESH THYME: Adds a peppery, herby flavor and pairs perfectly with sweet caramelized onions.
• GRUYERE CHEESE: Gruyere cheese is classic with French Onion Soup so I knew that it had to be a part of these crostini as well.
• BAGUETTE: You’ll only need 8 – 10 baguette slices for this recipe. I like to cut them on an angle at 1/2 inch thick.

Step by Step Photos and Instructions:

Making French Onion Crostini is easy! If you want to make the caramelized onions in advance and assemble just before serving that is a great time saver since it will take about 30 minutes for the onions.

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• STEP #1: Heat butter and olive oil in a skillet until butter has melted. Add onions and cook over low heat until they are browned and caramelized. This will take time, about 30 minutes.
• STEP #2: Place crostini slices on a baking sheet and rub with garlic clove.
• STEP #3: Spoon about 1 tablespoon of caramelized onions on top of each crostini. Season lightly with salt and pepper.
• STEP #4: Top with shredded Gruyere cheese. Place under the broil and broil for 1 – 2 minutes or until cheese has melted. Keep an eye on them to make sure they don’t burn. It can happen quickly.
• STEP #5: Top with fresh thyme leaves and serve immediately.

Storage and Leftovers:

I highly recommend eating these shortly after they are prepared. You can rewarm them in a warm oven until the topping is warmed through but you run the risk of the bread becoming overly crunchy.

Crostini are always great party appetizers, check out my other crostini recipes:

Pepperoni Pizza Crostini is perfect for the pizza lover in your life!

Goat Cheese and Chorizo Crostini is a favorite for warm summer days.

Turkey Brie Crostini makes a great use of Thanksgiving leftovers!