Ingredients
250g/9oz strong plain chocolate
100g/3½oz unsalted butter
150g/5oz caster sugar
150ml/5fl oz water
4 large egg, yolks only
500ml/17fl oz double cream

Method
1. Break up the chocolate and place with the unsalted butter in a warm-ish oven for about 15 minutes. Remove and stir until melted and blended together.
2. Over a low heat dissolve the sugar in the water then turn up the heat and boil rapidly for a few minutes to get a light syrup. It's ready before the syrup takes any colour, when a little dropped on to a cold plate forms a thread when stretched between finger and thumb. Leave the mixture to cool for just a minute.
3. Place the egg yolks in a basin and begin whisking (ideally with an electric whisk), trickling in the hot syrup as you go. Continue whisking until the mixture is thick and mousse-like. Whisk in the cream. Then fold in the melted chocolate and butter until thoroughly blended. Then pour the mixture into an ice cream machine and churn until frozen.