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Caramelized Onion and Gruyère Mini Tartlets with Thyme

Caramelized onion and Gruyère mini tartlets bake in puff pastry shells until golden, with soft sweet onions, creamy filling, and fresh thyme. These bite-size appetizers are baked in a mini muffin pan and served warm or at room temperature.
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Prep Time 20 minutes
Cook Time 57 minutes
Cooling 5 minutes
Total Time 1 hour 22 minutes
Servings: 24 servings
Course: Appetizer
Cuisine: French
Calories: 95
Ingredients Equipment Method Notes

Ingredients
  

For the caramelized onions
  • 1 tbsp unsalted butter
  • 1 yellow onion medium (about 8 ounces), thinly sliced
  • 0.25 tsp kosher salt
  • 1 tsp fresh thyme leaves chopped
For the tartlets
  • 1 nonstick cooking spray for coating the muffin cups
  • 1 package (17.3 oz) frozen puff pastry 2 sheets, thawed but cold
  • 1 tbsp all-purpose flour for rolling
  • 0.5 cup Gruyère cheese shredded
  • 2 eggs large
  • 0.25 cup heavy cream
  • 0.125 tsp black pepper

Equipment

  • 1 10-inch skillet
  • 1 24-cup mini muffin pan

Method
 

Make the onions
  1. Melt the butter in a 10-inch skillet over medium-low heat.
  2. Add the onion and salt; cook for 30–40 minutes, stirring every few minutes, until very soft and deep golden.
  3. Stir in the thyme and cook for 1 minute.
Prepare the pastry
  1. Heat the oven to 400°F and coat the cups of a 24-cup mini muffin pan with nonstick cooking spray.
  2. Lightly flour the work surface, unfold the pastry, and cut 24 rounds 2 1/2 inches across, rerolling scraps once if needed.
  3. Press one round into each muffin cup without stretching the pastry, then prick each base once or twice with a fork.
  4. Bake the shells for 8–10 minutes, until puffed and set.
  5. Gently press down the centers with the back of a spoon.
Assemble and bake
  1. Divide the Gruyère and caramelized onions among the shells.
  2. Whisk the eggs, heavy cream, and pepper together, then spoon the mixture evenly into the shells.
  3. Bake for 10–14 minutes, until the pastry is golden, the filling is set, and the centers reach 160°F.
  4. Cool the tartlets in the pan for 5 minutes before carefully lifting them out.

Notes

Keep the puff pastry cold while shaping for the best flaky shells. Store covered in the refrigerator for up to 3 days; baked tartlets can be frozen. Swiss cheese can replace Gruyère for a milder flavor.