Method

• 1.
  Place coffee, chocolate and butter in a heatproof bowl set over a pan of gently simmering water (don’t let the bowl touch the water), stirring until the chocolate and butter have melted. Remove bowl from heat and set aside.
• 2.
  Place yolks, whiskey, vanilla, 150g sugar and 1 tbs cold water in a separate heatproof bowl set over the simmering water (don’t let base of bowl touch the water) and whisk with handheld electric beaters for 3 minutes, or until thick and pale. Remove the bowl from the pan and sit in a larger bowl filled with iced water (don’t let any water get in the yolk mixture), then continue to whisk for a further 2-3 minutes, until the mixture thickens and cools slightly. Stir in the chocolate mixture until combined.
• 3.
  Whisk the egg whites in a clean bowl with a pinch of fine salt until soft peaks form. Add the extra 1 tbs sugar and beat until stiff and glossy.
• 4.
  Gently stir one-quarter of the egg white mixture into the chocolate mixture to loosen, then fold in the remaining egg white mixture until combined.
• 5.
  Spoon the chocolate mousse into small serving glasses, leaving a 2cm gap at the top. Chill for 3-4 hours to set.
• 6.
  Whisk thickened cream and Baileys together until stiff peaks form, then spoon over the mousse. Scatter with grated chocolate and serve chilled.