Despite what menu writers and produce marketers might want you to believe, every small potato is not a "new potato," and every new potato is not small. The real new potato — one that has just been dug and not dried — is a very special springtime treat.
To understand new potatoes, you need to know something about regular potatoes, which are grown and harvested with an eye toward long-term storage.
About 99% of all the potatoes you'll ever eat have been grown to maturity, dug from the ground and then "cured" — stored for a period of 10 days to two weeks in a climate-controlled environment. This toughens up the peel and reduces the amount of moisture in the potato to help it last longer without spoiling.
Truly new potatoes are sold right after they've been dug, without any curing. They're higher in moisture so they have a little creamier texture, and their flavor has, to my taste, a slight bitterness that complements their earthiness.
Though "new potato" is usually used to describe small potatoes, truly new potatoes can be any size, ranging from marbles to bakers.
Because these true new potatoes are such a special ingredient, treat them simply, at least the first time you serve them. One of my favorite things is just to steam them until tender, then toss them into softened butter you've whipped with fresh herbs and shallots. Stir just until the potatoes are evenly coated, sprinkle with coarse salt and serve.
How to choose: The best way to tell truly new potatoes is to rub the skin with your thumb — the peel should be delicate enough to scrape clean.
How to store: New potatoes can be stored at room temperature, but because they have not been cured, they won't last as long as regular potatoes — several days instead of several weeks. You can refrigerate them, but only for a couple of days — the cold will start converting the starch to sugar. New potatoes may look sweet, but you don't want them to taste that way.