Place the custard powder and vanilla flavour with 100ml of milk. Whisk to make a smooth paste and make sure no lumps form.
Boil the rest of the milk over a saucepan. While stirring, gradually pour agar-agar mix into boiling milk. Continue stirring and leave to boil for 2 minutes.
Remove the saucepan from the flame and add in custard mixture gradually while stirring.
Put the saucepan back to the flame and cook for 1 minute, stir continuously to avoid lumps in the custard.
Pour the mixture into moulds and refrigerate for 3 hours.
Garnish with red cherries when serving.