1. Preheat the oven to 400 degrees F. On a lightly floured surface, roll the puff pastry to a 13-inch-by-10-inch rectangle and transfer to a parchment-lined baking sheet. Prick the pastry all over with a fork and scatter with the leeks and both cheeses. Sprinkle with a pinch of kosher salt and 1/4 teaspoon pepper.
2. Bake until the pastry is a deep golden brown and the leeks are tender, 25 to 30 minutes. Cool for 10 minutes. Garnish with the chopped chives, cut into 16 or 24 pieces and serve.
From Food Network Kitchens