1.Preheat oven to 220°C/425°F. Grease oven trays.
2.To make choux pastry, combine the water, butter and sugar in a medium saucepan; bring to the boil (see page 112). Add flour; beat with a wooden spoon over medium heat until the mixture comes away from the base of the pan. Transfer pastry to a medium bowl; stand 1 minute. Beat in two of the eggs, one at a time, until pastry becomes smooth and glossy but still holds its shape.
3.Spoon pastry into piping bag fitted with a 1.2cm (½-inch) plain tube. Pipe 30 x 3cm x 4.5cm (1¼-inch x 1¾-inch) tear-shaped puffs, about 3cm (1¼ inches) apart, on trays; brush with lightly beaten remaining egg.
4.Bake puffs 10 minutes. Reduce oven temperature to 160°C/325°F; bake puffs a further 15 minutes. Turn off oven; cool puffs in oven with door ajar.
5.To make plain glacé icing, sift icing sugar into a small heatproof bowl; stir in enough water to make a thin paste. Stir over a small saucepan of simmering water until mixture is of a spreadable consistency. Cover surface with cling wrap until ready to use.
6.Using a serrated knife, cut off the top third of each puff. Remove and discard excess dough from centre. Place a small scoop of ice-cream into puff base; cover with puff top.
7.Using a small spoon, spread puffs with icing.
To pipe the puffs, place the tube close to the tray and press down to finish the choux with a small point.Note