To make them, puff pastry is rolled to 1/2 cm (1/4 inch) thick, then spread with a topping, then cut into rectangles 7 to 8 cm (3 inches) in width.
The pastry rectangles are then baked for 15 minutes at 200 C (400 F / gas mark 6.)
The toppings can be anything; Cooksinfo.com has listed some classical French versions.
New Larousse Gastronomique. Paris: Librairie Larousse. English edition 1977.