Place the chocolate in a bowl, pour over boiling water and leave to stand for approx. 2 mins. Carefully drain the water until only around 1 tbsp remains, stir the chocolate until smooth.
Combine the egg and sugar, stir well, continue stirring until the mixture is paler in colour and immediately stir well into the chocolate. Carefully fold the cream into the mixture using a rubber spatula, cover and chill for approx. 3 hrs.