Break the chocolate into a glass bowl suspended over a saucepan of simmering water. Melt the chocolate and stir often to make sure that no lumps form.
Remove the bowl from the heat and stir in the half-and-half, sugar, egg yolks and espresso.
In a clean bowl, whisk the egg whites to a stiff peak. Fold the egg whites into the chocolate mixture. Pour the chocolate mixture into individual shot glasses and place in a fridge for one hour or until they are set.
Once the mousse is set, top with whipped cream.
Serve with a grating of chocolate on top or a chocolate coated coffee bean.