7: Pour the mixture back into the saucepan (after washing it) and put back on low heat. Stir constantly and gently...
8: ...until the custard "coats" the spatula: you should be able to leave a clear trace with your finger, like in the photo. Take off the heat immediately and stand the saucepan in cold water, while continuing to stir for a few more minutes to stop the cooking. Your coffee custard is ready.
Remarks
For the coffee flavour, you can use instant coffee or a coffee extract instead of the ground coffee.