I recently bought something that was labelled at the grocery store as a "purple sweet potato". They were larger than what I am used to for sweet potatoes, but looked similar, although they had a purple skin on the outside and white flesh on the inside. I figured since they were labelled as "sweet potatoes", I would prepare them the same way I like to prepare regular sweet potatoes, by boiling them first (for about 40 minutes), then removing the skin, slicing it into wedges and then pan frying them. I have done this many times with normal sweet potatoes, and it works quite well.
However, after I boiled the purple sweet potatoes for 45 minutes, I pulled them out to take the skins off, and they were soft and stringy and incredibly off putting - they felt the same way as a gummy mashed potato would feel, and they fell apart all over the place.
Are they more like a potato, requiring less boiling time? Or is there something else going on here that I am missing?
Edit: I went to the grocery store today, and they are now labelled as "purple yams". I don't know if that makes a difference or not. I also got a picture of them, to make my description a bit clearer.