Caramelized Onion Tartlets with Brie

These elegant and delicious bite sized Caramelized Onion Tartlets with Brie are the perfect make-ahead party appetizer. Crispy phyllo cup shells are filled with savory and sweet caramelized onions and melty cheese creating an irresistible treat everyone will want more of.

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These Caramelized Onion Tartlets are a simple but elegant make-ahead appetizer perfect for a casual brunch or a dressed-up holiday party. Flakey phyllo cups filled with sweet and savory caramelized onions and melty cheese create a mouthwatering combination. There are only a few ingredients in these appetizer tartlets, but I promise your guests will keep coming back for more! 

I adore phyllo cup appetizers because they are so easy and versatile. Phyllo cup shells come frozen (already precooked) and only take a few minutes to crisp up in the oven. There are no limits to what fillings you can use in the tartlets. Since the phyllo cups come precooked, filling them after baking is also an option. These mini savory tarts are among my favorite recipes because you can caramelize the onions in advance, freeing even more time to entertain guests.

Caramelizing onions takes a bit of patience but is surprisingly easy to make. The natural sugars become released and caramelized when onions are allowed to cook low and slow. The flavor profile completely transforms into an addicting sweet and sticky mixture. Not only are they simple, but they are incredibly delicious. It becomes difficult to resist eating them with a fork out right out of the pan! If you love them as much as I do, you'll love this post featuring 17 Ways to Use Caramelized Onions.

Ingredients

Frozen Phyllo Cup Shells: Fresh phyllo pastry sheets are notoriously difficult to work with. Thankfully, you can purchase precooked frozen phyllo cup shells at most major grocery stores, which could not be easier. They work with just about any filling you can imagine and make the perfect appetizer tartlets.  

Yellow Onions - Sweet yellow onions work best for this onion tartlet recipe. It may seem like a large number of onions, but as they cook, the moisture is released, and their volume shrinks considerably.

Brie Cheese - Just about any cheese you can think of would be delicious in these caramelized onion phyllo cups. Goat cheese or even feta cheese would make great alternatives.

Vegetable or Chicken Broth - Broth is used to deglaze the pan while the onions cook. The broth ensures the onions do not dry out and burn while cooking low and slow.

Olive Oil - We prefer using extra virgin olive oil in this recipe. 

Butter - Use unsalted butter to control the amount of salt. It's always possible to add more salt. However, it isn't easy to salvage an overly salty dish.

Fresh Thyme - Fresh thyme adds a beautiful pop of color and fresh taste to this appetizer tartlet recipe.

How to Make Caramelized Onion Mini Tarts

Caramelizing The Onions

1. First, thinly slice the onions and add them to a sauté pan with olive oil and butter. Like many others, slicing onions makes my eyes water like crazy. I have found these onion goggles work wonders if this happens. They might make you look funny, but they sure make slicing onions much easier! 
2. Next, cook the onions over medium to medium/low heat, stirring every 5 minutes for 35 to 45 minutes. At this point, if the onions become too dry in the pan, add a small amount of chicken or vegetable broth to keep them moist. 

3. Continue sautéing the onions for 15 to 30 more minutes until the color slowly turns from golden brown to a deep amber color. The onions will continue to darken the longer they cook. You will also notice the volume of onions has significantly reduced and become a mix of sticky, sweet brown deliciousness. Once done, add salt to taste.
4. Place the caramelized onions in a bowl and set aside. If making in advance, place the onions in an airtight container and refrigerate until ready to use.

Making the Caramelized Onion Tartlets

5. Preheat your oven to 350ºF. Then, remove the phyllo cup shells from the package and place them on a large baking sheet. 
6. Next, fill each phyllo shell with about one teaspoon of creamy brie cheese and bake for five minutes. 

7. Remove the tartlets from the oven and top with about half a teaspoon of caramelized onions. 
8. Finally, garnish the cheese and onion tartlets with fresh thyme. Serve warm or at room temperature.

Variations and Substitutions

Use a different cheese - Just about any cheese works with this recipe. I prefer a creamy cheese; however, onion tartlets with goat cheese or feta cheese would be as delicious. 

Bourbon caramelized onions: While the onions are caramelizing, add a splash of bourbon to the mixture and allow the alcohol to cook-off. What will be left is a subtle, delicious bourbon flavor.    

Vegan caramelized onion tartlets: Omit the butter and cheese and use vegetable broth to make this tartlet appetizer vegan. Add some chopped mushrooms sauteed in olive oil for a delicious twist in place of cheese.

Tips For This Recipe

• Using four large onions will seem like a large amount. Make sure to use the full amount the recipe calls for as they cook down in volume significantly. 
• Add broth to prevent burning if the onions look like they may be drying out while cooking. Add a tablespoon of chicken broth or vegetable broth to deglaze the pan and prevent the onions from becoming too dry. 

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