Have you tried these?

The Little Potato Company says they are not immature regular potatoes but are instead a particular variety of potato that stays small. On the net I see them described as baby Yukon Gold or Red potatoes.

I've tried Little brand and some others just sold as "miniature potatoes" and I can't tell the difference? I can tell you that they are really delicious, especially roasted. Lots of "potato" flavor and less starch than big potatoes.

Recipes here.