Pour the measured water into a medium saucepan, add the butter and salt and heat until the butter has melted. Bring up to the boil, then take off the heat and stir in the flour. Put the pan back on the heat and cook briefly, stirring until the mixture makes a smooth ball. Leave to cool.
Beat the eggs and vanilla essence together, then gradually beat into the flour mixture until smooth. Spoon the mixture into a large piping bag fitted with a 1.5 cm (¾ inch) plain piping tube. Lightly grease a large baking sheet then pipe on 20 balls, leaving space between them.
Bake in a preheated oven, 200°C (400°F), Gas Mark 6, for 15 minutes until well risen. Make a slit in the side of each ball for the steam to escape, return to the turned-off oven for 5 minutes, then take out and cool.
Make the sauce by heating the chocolate, milk and sugar in a saucepan and stirring until smooth. Take off the heat and mix in the brandy.
Whip the cream until it forms soft swirls, fold in the ginger, then enlarge the slit in each profiterole and spoon in the ginger cream. Pile into serving dishes and drizzle with reheated sauce.