Add the gelatin to a small bowl of iced water and set aside for 5 minutes to bloom. Once softened, squeeze out excess water and set aside. Chop the 200g chocolate, place in a large bowl and set aside.
Meanwhile, add the egg yolks, milk and sugar to a small saucepan and whisk to combine. Cook, stirring, until the mixture reaches 75C or has thickened slightly. Take care not to overheat the custard as the yolks will curdle. Add the softened gelatin and stir to dissolve.
Pour the warm custard through a sieve to remove any egg white and undissolved gelatine over the bowl of chocolate, and stir until the chocolate has melted. If it doesn’t melt completely, microwave it on medium in 30-second bursts until melted.
Set the chocolate mixture aside to cool for 30 minutes to an hour before folding through the cream. When touched with a fingertip, the mixture should have no remaining warmth.
Whisk the cream until soft peaks form, then gently fold it through the cooled chocolate mixture using a whisk (see note).
Transfer the mousse to the fridge to set for 2-3 hours before piping into serving glasses using a large star tip. You could also set the mousse directly into serving glasses, if you prefer. Shave a little chocolate over each dish using a vegetable peeler to serve.
