Put the cream, milk and coffee in a saucepan over a low heat until it starts to simmer, then remove from the heat.
Meanwhile beat egg yolks and sugar in a bowl until pale and thick. Once coffee cream is hot, slowly pour into the egg mixture, whisking all the time to prevent the egg scrambling.
Wipe out the pan and pour this mix back in. Stir over a low heat. Keep cooking gently until thickened, and when you drag your finger over the back of the stirring spoon it leaves a clear ridge. This will take 3 - 6 minutes. Transfer this to a jug to chill.
When chilled, churn in your ice cream machine until smooth and creamy. If you don't use an ice cream machine, put the mix in a tub in the freezer and churn it up with a fork every 30 minutes or so until set.