Bring the water to the boil in a large saucepan. Add the butter, salt and nutmeg and, when the butter has melted, remove from the heat and gradually beat in the flour. Continue beating until the dough comes away from the sides of the pan.

One by one, beat the eggs into the mixture, making sure each is absorbed before adding the next. When the eggs have been added, the mixture should be thick and glossy.

Preheat the oven to hot 220°C (Gas Mark 7, 425°F). Lightly grease two baking sheets.

Fill a forcing bag, fitted with a plain nozzle, with the pastry dough. Squeeze the dough on to the baking sheets in circular mounds (about 5 cm (2 in) in diameter and 2 1/2 cm (1 in) in height). If you do not have a forcing bag, arrange the dough carefully into mounds on the sheets, using two spoons. The puffs will expand considerably in baking, so allow plenty of space between each one. Coat each puff with the beaten egg mixture and put the sheets into the oven. Bake for 10 minutes. Reduce the oven temperature to fairly hot 190°C (Gas Mark 5, 375 °F) and bake the puffs for a further 25 to 30 minutes, or until they have doubled in size and are light brown in colour.

Remove from the oven and make a slit in the side of each puff to allow the steam to escape. Replace the puffs in the turned-off oven for 10 minutes, then transfer to a wire rack to cool to room temperature.

Cut the tops off the puffs and reserve. Fill the puffs with the ice-cream. Replace the tops and arrange the filled puffs on a serving dish.

Pour over the melted chocolate and serve at once.