This is a frothy, soft, white ice with a lemony tang, which is streaked with dark chocolate. It is quite quickly made and is irresistible for any occasion, from a family lunch to a sophisticated dinner party.
To make the chocolate, put the hot water into a bowl set over a saucepan of very hot, but not boiling, water. Add the instant coffee and caster sugar, stir, and then add the chocolate. Stir the mixture in the bowl until completely smooth. Add the egg yolks one at a time. Continue stirring over the hot water for about 5 minutes. Then put the bowl on one side to cool.
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