Servings: Makes 4 servings
Ingredients 2 1/2 cups all-purpose flour2 sticks unsalted butter , cut into small pieces1 teaspoon kosher salt1 teaspoon sugar4 to 6 tablespoons ice water1 egg yolk1 tablespoon heavy cream2 tablespoons olive oil1 tablespoon unsalted butter3 large Vidalia onions , thinly sliced1 tablespoon thyme1 to 2 teaspoons black pepper
In a food processor, combine flour, butter, salt, and sugar; pulse until it forms a coarse meal. Continue pulsing and add water, 1 tablespoon at a time, until meal moistens into dough. Form dough into disc; wrap in plastic. Refrigerate at least 30 minutes.
Meanwhile, in a large sauté pan over medium flame, heat oil and butter. Once hot, add onions; cook slowly until golden brown, about 25 minutes. Stir in thyme, salt, and pepper. Set aside.
Preheat oven to 375°F. Roll out dough on a floured piece of parchment into 14- to 15-inch circle. Place cooled onion mixture in center, fold over edges about 2 inches. In a small bowl, combine egg yolk and heavy cream; brush mixture over edges of dough. Bake until golden brown, 20 to 25 minutes. Serve warm.