There is no such thing as an “all-purpose potato”. In general there are two basic types: waxy and floury. Waxy potatoes have 13-15% starch, floury potatoes have more, 20-22%. At the St. Lawrence Market, there is a farmer at the farmers market on Saturday mornings, Robert Taylor, whose farm, The Potato Patch at Cedar Creek Farm, produces some of the best potatoes – almost 80 varieties worth. And they are not run-of-the-mill potatoes – some old heirloom varieties from Germany and France in the late 1800s. They have fancy names like Viking, Linzer, Kennebec, Carola, Chieftain, Nicola, German Butterball, and Vivaldi. They are sold in basket, and still have dirt on them.
Here are some of my favourites:
Elba: A white fleshed medium starch potato, great for mashing.
Cecile: A yellow fleshed potato that is great for sautéing, or in stews, pan-fried.
Bintje: Developed in the Netherlands in 1904. They have a pale yellow flesh and are good for french fries, mashing, and making gnocchi.
Looking for a source on potatoes? Check this out: Kenosha Potato Collection Catalog.