How to write the so called wooden tomato / wooden potato in Chinese (and where to find it)

chinese-cuisinelanguagepotatoesroottomatoes

I once went to a Chinese restaurant with a Chinese friend, and there was this sort of yam which was white colored and covered with a whole bunch of red/pink dots resembling freckles and these dots would be found inside of it whenever cut. This food was then boiled in a pot of water and other stuff on the table and once soft it could be eaten just like a yam or potato and was very delicious.

My friend said in Chinese it's called wooden potato or wooden potato (something like "mu shu", perhaps 木薯). However, I wasn't able to find this anywhere on the Internet (or, at least, I was not able to find the one with all the red/pink freckles). Anyone know what this kind is properly called (in Chinese and in English), where to find more information about it, and where to buy it?

Thanks.