Serve this savory puff pastry tart as an elegant appetizer or a vegetarian main.
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This simple, yet impressive savory tart combines cheese, potatoes, and thyme on a crispy puff pastry crust. Using store-bought puff pastry and a bit of Dijon mustard makes this tart easy enough for a weeknight but impressive enough for company. Cut the tart into 16 pieces for an elegant appetizer or slice into larger wedges and serve it with a salad for a light lunch, or holiday vegetarian main.
Notes from the Food & Wine Test Kitchen
The potatoes need to be just tender but not completely soft when they are first boiled. If they get completely soft, they are a lot harder to cut into slices.
While caramelizing the onions in Step 2, make sure each time you remove the lid to stir, you let the droplets of condensation fall back into the onions in order to keep the heat and stem inside the pan. This helps the onions caramelize faster.
Make ahead
You can shred the cheese in advance and store it in a ziplock plastic bag. You can also parboil the potatoes up to three days ahead. Let them completely cool before refrigerating them. When you are ready to use them in the tart, peel and slice the potatoes and proceed with the recipe. You can also make this tart in advance; wrap the tart in plastic wrap and store it in the refrigerator for up to three days. Reheat it in an air fryer or oven preheated to 400 °F for five minutes.
Ingredients
- 1 pound medium-size (about 4 ounces each) Yukon Gold potatoes, scrubbed and cut into 1/8-inch slices
- 2 tablespoons, plus 1/4 teaspoon kosher salt, divided
- 2 tablespoons extra-virgin olive oil
- 1 large yellow onion, thinly sliced
- 2 tablespoons water
- 1 frozen puff pastry sheet (from 1 [17.3-ounce] package), thawed
- All-purpose flour
- 1/4 cup heavy whipping cream
- 2 tablespoons fresh thyme leaves, plus more for garnish
- 1 teaspoon Dijon mustard
- 1/8 teaspoon ground nutmeg
- 6 ounces Gruyère cheese, shredded (about 1 1/2 cups), divided
- Black pepper
Directions
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Preheat oven to 400°F with rack in lower third position. Line a rimmed baking sheet with parchment paper. Place potatoes and 2 tablespoons of the salt in a large saucepan; add water to cover by 1 inch. Bring to a boil over high; reduce heat to medium, and cook, undisturbed, until potatoes can be pierced using tip of a knife but are still firm, 2 to 3 minutes. Drain well; let stand until cool enough to handle, about 10 minutes.
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Return saucepan to medium heat; add oil, and heat until shimmering. Stir in onion and remaining 1/4 teaspoon salt; cook, stirring occasionally, until translucent, about 3 minutes. Reduce heat to medium-low; cover and cook, stirring occasionally, until onion begins to soften and brown around edges, about 18 minutes. Uncover and increase heat to medium-high; stir in water, scraping up any browned bits from bottom of saucepan. Cook 2 minutes, stirring often, until onion is browned and caramelized. Let stand until cool, about 5 minutes.
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Roll puff pastry on a lightly floured work surface to a 14- x 12-inch rectangle. Transfer to prepared baking sheet. Lightly score a border around perimeter of puff pastry using a paring knife, about 1 inch from edges. Prick pastry all over using a fork, leaving a 1-inch border around edge.
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Stir together cream, thyme, Dijon mustard, nutmeg, and 1 cup of the Gruyère in a medium bowl until combined. Spread cheese mixture in an even layer inside scored border of pastry. Arrange potato slices in overlapping layers over cheese mixture inside border; top evenly with caramelized onions. Top with remaining 1/2 cup Gruyère.
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Bake in preheated oven until pastry is puffed and deep golden brown, about 30 minutes. Transfer baking sheet to a wire rack, and let cool 5 minutes. Garnish with black pepper and additional thyme. Slice into 16 (3 1/4- x 3-inch) pieces; serve warm or at room temperature.