I'm not Australian, but in general food imports are restricted only for fresh/preserved foods that could potentially carry some kind of bacteria, virus, insects or that could contain seeds that could germinate a non-native plant accidentally: seeds, nuts, meat, eggs, dairy, fruit/veg, etc. I think packaged foods like chocolate or cookies wouldn't normally be a problem.
This page might be helpful, it lists restricted food items for import into Australia:
http://www.daff.gov.au/aqis/travel/e...alia/cant-take