(麻薯), what kind, if not then what is it?
麻薯 or 麻糬 is the transcription of Japanese desert "Mochi/もち".

The character 薯 means root vegetables.
Most of time it will be potato.

Some examples:

馬鈴薯 potato
蕃薯 sweet potato
木薯/樹薯 cassava