French onion tartlets are a savory holiday appetizer made with flaky puff pastry, caramelized onions, and melted Gruyère cheese, perfect for Thanksgiving, Christmas, or New Year's.
Ingredients
- Butter
- Olive Oil
- Large Yellow Onions
- Salt
- White Granulated Sugar
- Worcestershire Sauce
- Dried Thyme
- Black Pepper
- Beef Broth
- Puff Pastry Sheets
- Large Egg
- Water
- Gruyère Cheese
- Fresh Thyme, optional
How to Make French Onion Tartlets
- Add butter and olive oil to a large skillet over medium-low heat. Add the onions and season with salt. Cook for 30-40 minutes, stirring occasionally, until the onions are deeply golden and caramelized. Drain any excess grease from the pan. Add sugar and let it become jammy.
- Add the Worcestershire sauce, thyme, black pepper, and beef broth. Cook for another 3-5 minutes, until the liquid has mostly evaporated.
- Preheat the oven to 400°F. Line 2 baking sheets with parchment paper or silicone baking mats.
- Roll out the puff pastry sheets to 9×12-inch rectangles. Use a 2 ½ to 3-inch circle cookie cutter or pastry cutter to cut circles out of the sheets. Avoid going smaller than this because they will shrink as they bake.
- Place the circles on each of the prepared sheets. Pierce the circles with a fork to prevent air bubbles as they bake. Brush each circle with egg wash (1 egg + 1 tablespoon of water, scrambled).
- Bake for 6 minutes, until they are puffed up. Remove from the oven and use a small circle, like the bottom of a shot glass, to indent each puff pastry. If you can’t find a small circle, use the back of a spoon. Be sure not to press all the way through.
- Fill the center of each circle with caramelized onions. Top each with shredded gruyère cheese.
- Bake for 5-6 minutes, until the cheese is melted and the shells are crisp.
- Garnish with fresh thyme, if desired.
Tips
Caramelize the onions slowly. Medium-low heat gives you deep, sweet onion flavor without burning them. Don't rush this step by turning the heat too high.
Cook off excess moisture. The onion mixture should be thick rather than watery before filling the tartlets, or the pastry can turn soggy.
Let the filling cool slightly before spooning it into puff pastry. Very hot filling can soften the pastry before it reaches the oven.
Keep puff pastry cold. Work with it while it's still chilled so the layers puff properly and stay flaky.
Don't overfill the tartlets. Leave a little room around the edges so the pastry can rise instead of getting weighed down.
Use Gruyère for the classic French onion flavor. Swiss is a good substitute, and mozzarella can be mixed in if you want a milder, stretchier cheese.
They're best served warm. If making them ahead, reheat them in the oven or air fryer rather than the microwave so the pastry crisps back up.
For holiday prep, make the onion filling ahead. It can be refrigerated for a couple of days, then you can assemble and bake the tartlets closer to serving time.
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French Onion Tartlets
Ingredients
- 3 tablespoons Butter
- 1 tablespoon Olive Oil
- 2 Large Yellow Onions thinly sliced
- Salt to taste
- ½ teaspoon White Granulated Sugar
- 1 teaspoon Worcestershire Sauce
- ½ teaspoon Dried Thyme
- ¼ teaspoon Black Pepper
- ¼ cup Beef Broth
- 2 Puff Pastry Sheets thawed
- 1 Large Egg
- 1 tablespoon Water
- ½ cup Gruyère Cheese shredded
- Fresh Thyme optional for garnish
Instructions
- Add butter and olive oil to a large skillet over medium-low heat. Add the onions and season with salt. Cook for 30-40 minutes, stirring occasionally, until the onions are deeply golden and caramelized. Drain any excess grease from the pan. Add sugar and let it become jammy.
- Add the Worcestershire sauce, thyme, black pepper, and beef broth. Cook for another 3-5 minutes, until the liquid has mostly evaporated.
- Preheat the oven to 400°F. Line 2 baking sheets with parchment paper or silicone baking mats.
- Roll out the puff pastry sheets into 9×12-inch rectangles. Use a 2 ½ to 3-inch circle cookie cutter or pastry cutter to cut circles from the sheets. Avoid going smaller than this because they will shrink as they bake.
- Place the circles on each prepared baking sheet. Pierce the circles with a fork to prevent air bubbles as they bake. Brush each circle with egg wash (1 egg + 1 tablespoon of water, scrambled).
- Bake for 6 minutes, until they are puffed up. Remove from the oven and use a small circle, like the bottom of a shot glass, to indent each puff pastry. If you can't find a small circle, use the back of a spoon. Be sure not to press all the way through.
- Fill the center of each circle with caramelized onions. Top each with shredded gruyère cheese.
- Bake for 5-6 minutes, until the cheese melts and the shells are crisp.
- Garnish with fresh thyme, if desired.
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