In a saucepan, combine: Milk, Sugar, Fresh cream, Coffee mixture, Cornflour. Whisk well before heating.
Cook on medium-low heat, whisking continuously until thick and smooth (custard-like).
Add: Butter, Vanilla. Mix until glossy.
Turn heat low or off, add chocolate, rest briefly, then whisk until smooth. Gently reheat if needed.
Strain and blend until ultra smooth.
Refrigerate until pipeable consistency.