Top these flaky pastries with your favorite tartlet ingredients.
Preheat the oven to 375°. Prepare your toppings.
Roll the puff pastry sheets out to 10-by-12-inch rectangles. Cut each sheet into eight 3-by-5-inch rectangles. Using the tip of a sharp knife, lightly score a 1/2-inch border on each pastry rectangle. Using a fork, pierce the inner rectangle all over (this will prevent the center from puffing up as the pastry bakes). Lightly brush the pastries with the egg. Bake until puffed and light golden, about 15 minutes.
Arrange the toppings on the inner rectangle. Bake until the toppings are hot and the pastry is cooked through, 5 to 7 minutes longer. Serve warm or at room temperature.