Anton Edelmann, maitre chef des cuisines at the Savoy in London, serves these luxurious biscuits at afternoon tea.
On a lightly floured surface, roll puff pastry to a 1/8-inch thickness, and trim to a 2-by-12-inch rectangle. Transfer to a baking pan. Prick well with a fork, and chill for 20 minutes.
In a small bowl, beat egg white and confectioners' sugar together with a wooden spoon until smooth. Using a small offset spatula, spread a thin layer onto the chilled pastry. Freeze for 25 minutes.
Preheat oven to 425 degrees. Remove iced pastry from freezer. Using a damp knife, cut vertically into sixteen 3/4-inch fingers. Transfer to a baking pan. Bake until pastry is golden and icing is curled up at ends, about 15 minutes. Transfer to a wire rack to cool.