Potato-Gruyère Tart
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