If you love French Onion Soup, these cheesy Caramelized Onion Tartlets will be your new favorite appetizer! With caramelized onion, fresh thyme, and Gruyere cheese they have the same flavor profile as the soup, but with a buttery extra flaky crust.
As we move into fall, most of us have heartier foods on our minds. Soups and stews, casseroles, pies, and cookies. Foods that bring families together, and foods that we can share with friends.
I love whipping up a batch of cookies or baking up a pie this time of year. There’s just something about the cool, crisp air and colorful leaves that puts me in the mood to spend an afternoon in the kitchen creating something beautiful and delicious.
And let’s not forget that baking season doesn’t have to mean a sweet treat. These bite-sized French Onion Soup-inspired Caramelized Onion Tartlets are easy to whip up when you want to bake!
These tartlets have a secret ingredient: a touch of cornstarch in the crust makes them extra crisp and flaky!
With a rich, buttery, crisp crust and a savory cheesy onion filling, these cheese and onion tartlets will be your favorite new appetizer or addition to brunch. Bookmark the recipe now for the holidays because they’ll be here before we know it.
Heads-up, these make a perfect little nibble to serve on Thanksgiving before the turkey dinner!
Caramelized Onion Tartlets Recipe
This recipe for French Onion Tartlets really only has three main steps:
- Make the dough for the crust.
- Caramelize the onion and mix together the couple ingredients for the filling.
- Bake!
If you usually opt for premade pie crust, don’t be intimidated to make your own. I’m going to show you just how easy it really is. However, if you're pressed for time you can always use store-bought pie dough or puff pastry to make these onion tarts (look for both of them in the frozen dough aisle).
Caramelizing onion is as easy as cooking onion low-and-slow in a heavy skillet. The cooking process does all the work and magically melts the onion down, transforming it to something sweet and savory.
The filling for these cheese and onion tartlets is similar to a savory quiche, with a cream, egg, and cheese base in addition to the caramelized onion. A flavorless cornstarch slurry (basically a mixture of cornstarch and cold water) helps it to thicken and set.
Ingredients
In these sections I explain the ingredients and give substitution ideas. For the full recipe (including ingredient amounts), see the recipe card below.
Crust Ingredients
- Flour - we use all-purpose flour as the base of this crust
- Cornstarch - this the key ingredient that makes our all-butter crust extra crisp and flaky
- Salt - to make sure our dough isn't bland
- Unsalted butter - make sure it's very cold for the flakiest crust, and make sure to dice it small
- Water - we want ice cold water for making pie crust, which helps keep the butter cold
Caramelized Onion Filling Ingredients
- Unsalted butter - we use this to caramelize our onions for a rich, deep flavor
- Onion - yellow onion works great here
- Salt and black pepper - to season our mini tarts
- Garlic - for savory flavor
- Fresh thyme - in a pinch you can use half the amount of dried thyme leaves instead
- Eggs - eggs help create a quiche-like filling for our tartlets
- Heavy whipping cream - for richness and to achieve the right texture
- Cornstarch - dissolved in cold water to make a slurry
- Gruyere cheese - or other Swiss cheese
How to Make Pie Crust From Scratch
To start, get out the ingredients to make pie crust: all-purpose flour, cornstarch (this is the key to a crisp crust!), salt, butter, and ice water.
- Whisk together the flour, corn starch, and salt, and then use a fork or pastry cutter to cut in the diced butter.
- Work in enough ice water so that it forms a dough and you can squeeze it into a ball.
- Shape the dough into a disk, wrap it in plastic wrap, and refrigerate to chill, about 30 minutes to 1 hour. Or you can chill the dough for up to 3 days and let it sit at room temperature for about 15 minutes before rolling it out.
- Roll out the dough on a lightly floured surface to a circle about 14 inches in diameter.
- Use a 3-inch cookie cutter (or a glass with that diameter) to stamp out circles in the dough. Gather the scraps of dough, re-roll them, and continue stamping out circles until the dough is gone.
- Press each dough circle into the well of a mini muffin tray.
Now you’re ready to fill the tart shells to make these Caramelized Onion Tartlets!
How to Caramelize Onion and Make the Filling for These Tartlets
- Peel and thinly slice onion.
- Cook the onion with a pat of butter in a heavy-bottomed skillet (I like to use cast-iron) over medium heat until the onion is melted down into a rich golden brown color. Stir frequently and turn the heat down or add a splash of water as necessary to prevent the onion from burning. Let the caramelized onion cool.
- Whisk together the eggs, cream, and corn starch slurry in a large bowl, and then whisk in the cooled caramelised onion. Whisk in the cheese.
Caramelized onion is one of the star ingredients in the filling of our French Onion Tartlets recipe. And heads-up, make a double batch because you can slather caramelized onion on top of burgers, add them to grilled cheese, or use them to whip up an omelet!
How to Bake Mini French Onion Tarts
Once you have the dough pressed into the wells of a mini muffin pan and the caramelized onion filling made, just add about 1 tablespoon of filling to each tart and then bake!
These cheese and onion tartlets are done when the crust is golden and the filling is set. They take about 25 to 30 minutes at 375F.
Storage and Reheating
Store these tartlets wrapped in the fridge for up to 5 days.
To reheat these cheese and onion tartlets, place them on a baking tray and heat in a 375F oven until warm, about 8 minutes.
Caramelized Onion Tartlets FAQs
Can I Use Puff Pastry to Make This Recipe?
Yes! In a time crunch, puff pastry is the next best thing.
Let the puff pastry thaw, roll it out so it's an even thickness, and then stamp out 3-inch circles. Continue on with the rest of the recipe as written.
Can I Use Store-Bought Pie Crust to Make This Recipe?
Absolutely. If your pie dough is frozen, let it thaw, roll it out to an even thickness, stamp out circles, and proceed.
What Type of Onion Can I Use?
My favorite kind of onion to use to make caramelized onion is yellow onion. It has a sharp bite that mellows out when it's caramelized, but unlike sweeter onions (such as Vidalia), caramelized yellow onion isn't overly sweet.
If you don't have yellow onion on hand, red onion will also work well here.
More Bite-Sized Appetizers to Try
- Spanakopita Puff Pastry Bites
- Turkey Sausage Meatballs with Sugar Free Cranberry Sauce
- Date and Walnut Crispbread with 3 Brie Topping Ideas
Let's Connect
Did you make this recipe? Please rate it and leave a comment below. You can also tag @anediblemosaic on social media.
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Caramelized Onion Tartlets Recipe
Equipment
Ingredients
Crust:
- 2 ¼ cups all-purpose flour plus more for rolling out the dough
- ¼ cup cornstarch
- ¾ teaspoon salt
- 1 cup unsalted butter chilled and diced
- ¾ cup ice-cold water plus more as needed
Filling:
- 2 tablespoons unsalted butter
- 3 small-medium yellow onions peeled and thinly sliced
- ½ teaspoon salt
- ½ teaspoon black pepper
- 1 clove garlic peeled and crushed
- 1 teaspoon minced fresh thyme leaves
- 2 large eggs
- ¼ cup heavy whipping cream
- 4 teaspoons cornstarch dissolved in ¼ cup cold water to make a slurry
- 4 ounces Gruyere cheese shredded
Instructions
For the Crust:
- Whisk together the flour, corn starch, and salt, and then use a fork or pastry cutter to cut in the diced butter.
- Adding 2 tablespoons of ice-cold water at a time, work in enough water so that it forms a dough and you can squeeze it into a ball.
- Shape the dough into a disk, wrap it in plastic wrap, and refrigerate to chill, about 30 minutes to 1 hour. Or you can chill the dough for up to 3 days and let it sit at room temperature for about 15 minutes before rolling it out.
For the Filling:
- Add the butter to a large, heavy-bottomed skillet over medium heat.
- Once melted, add the onion and cook until the onion is melted down into a rich golden brown color, about 35 to 45 minutes. Stir frequently and turn the heat down or add a splash of water as necessary to prevent the onion from burning.
- Add the salt, black pepper, garlic, and thyme and cook 1 minute more, stirring constantly. Cool.
- Whisk together the eggs, cream, and corn starch slurry in a large bowl, and then whisk in the cooled caramelized onion. Whisk in the cheese.
To Assemble and Bake the Tartlets:
- Preheat the oven to 375F.
- Roll out the disk of dough on a lightly floured surface to a circle about 14 inches in diameter.
- Use a 3-inch cookie cutter (or a glass with that diameter) to stamp out circles in the dough. Gather the scraps of dough, re-roll them, and continue stamping out circles until the dough is gone.
- Press each dough circle into the well of a mini muffin tray. Fill each tart with 1 tablespoon of caramelized onion filling.
- Bake until the crust is golden and the filling is set, about 25 to 30 minutes.
- Let the tartlets cool until you can handle them, and then pop each one out of the mini muffin tray.
- Serve warm or at room temperature.
Faith's Tips
- Recipe Yield and Serving Size: This recipe makes 48 tartlets for a total of 12 servings. Each serving is 4 tartlets.
- Storage: Store these tartlets wrapped in the fridge for up to 5 days.
- Reheating: To reheat these tartlets, place them on a baking tray and heat in a 375F oven until warm, about 8 minutes.
Nutrition
Alicia says
These sound like the tartlets I love getting from trader joe's. Could you put feta or brie in these to recreate those?
Faith says
Alicia, Yes, you could definitely add cheese to the filling, I think it would be delicious!