Preheat the oven to 200 degrees C. Lightly grease baking trays.
In a medium bowl cream together the butter and sugar until smooth. Beat in the egg whites one at a time until batter is light and fluffy. Stir in the vanilla. Mix in the flour just until blended. Dough will be a little stiff. Force through a pastry bag with a medium star tip onto lightly buttered baking trays. Make each biscuit about 8cm long.
Bake for about 10 minutes in the preheated oven until straw-coloured. When cool, dip one end of each biscuit in melted chocolate and place on wax paper until chocolate hardens. Store in a cool place.