Spinach-Sorrel Tarts

Black-Pepper Pate Brisee: Preheat oven to 400 degrees, with rack in lowest position. Pulse flour, sugar, salt, and pepper in a food processor until combined. Add butter, and process until mixture resembles coarse meal, about 10 seconds. Drizzle 1/4 cup ice water over mixture. Pulse until mixture holds together when pressed between 2 fingers. If dough is too dry, add more water, 1 tablespoon at a time, and pulse. Shape dough into 2 disks, and wrap each in plastic wrap. Refrigerate dough until firm, at least 1 hour and up to 2 days.

Filling: Heat oil in a large saute pan over medium heat. Cook onions, garlic, and red-pepper flakes until onions are softened and just starting to turn golden, about 10 minutes. Add spinach and sorrel, and cook, stirring with tongs, until greens just wilt, about 2 minutes. Let cool.

Assembly: Roll out each piece of dough to an 11-by-14-inch rectangle on lightly floured parchment, and transfer to 2 baking sheets. Divide filling between rectangles, leaving a 2-inch border all around. Season filling with salt, and fold in edges of dough. Refrigerate 1 tart, and bake the other until edges are golden, about 35 minutes. Place half the cheese on top of filling, and bake until cheese is melted, 5 minutes more. Bake remaining tart in same manner. Serve tarts warm or at room temperature.