Preheat the oven to 140°C/275°C/Gas mark 1. Line a baking tray with greaseproof paper.
Whisk the egg white until stiff. Gradually whisk in half of the sugar, then fold in the remainder with the cornflour and chocolate.
Transfer the mixture to a piping bag with a large star nozzle, and pipe 6.5cm/2 1⁄2in nests onto the baking tray.
Bake in the oven for 45 minutes. Leave to cool, then fill with mini chocolate eggs.