The best chocolate mousse

Put the chocolate into a large heatproof bowl set over a saucepan of just-simmering water. Allow to melt, stirring occasionally until smooth, then remove from the heat and allow to cool to room temperature.

Separate the egg, placing the white into a clean mixing bowl. Add the yolk to the chocolate. Stir to combine.

Using an electric hand mixer, whip the egg white until it forms soft peaks. Add the caster sugar and briefly whisk again. Add 1/3 of the whisked egg white into the chocolate mixture and mix well. This loosens up the mixture so it is easier to incorporate the rest of the whites without knocking out too much air. Add the remaining white and carefully fold through in a figure of 8 motion, using a spatula until no white patches of egg remain.

Pour the double cream into the mixing bowl used to whisk the egg white (no need to wash it) and whip to soft peaks using the hand mixer. Gently fold the whipped cream into the mousse until just combined, taking care not to overmix. Fold through the Baileys, if using.

Put a dollop of salted caramel into the bottom of 4 small glasses or ramekins, then spoon in the mousse mixture. Cover and chill for at least 3 hours. Once set, remove from the fridge 5 minutes before serving. Top with the extra 50ml cream, whipped, if liked. Keep in the fridge for up to 3 days.