In a dry bowl add in your butter & powdered sugar mix together until fulfy,add your egg, flavor and mix again

Pour in your custard powder, flour & baking powder & mix the consistency will be thick then add in your liquid milk little at a time, until it give you a piping consistency I.e not too thick and not not watering

Put your nozzle in the piping bag & pour in your mixture, pipe it in a baking tray & bake for like 10 - 15 mins in a low heat