Cynthia is my sister-in-law’s mother; she’s a wonderfully kind woman and she often makes this lovely, rich chocolate cake when you go to visit. It will keep for 3 to 4 days in an airtight tin.
Put the chocolate into a pan with the butter. Mix the coffee granules with 125ml just-boiled water and add to the pan, then put it over a low heat until the chocolate and butter are just melted.