MASHED POTATOES

POTATOES ARE COMPOSED MOSTLY OF STARCH and water. The starch is in the form of granules, which in turn are contained in starch cells. The higher the starch content of the potato, the fuller the cells. In high-starch potatoes, the cells are completely full—they look like plump little beach balls. In medium-and low-starch potatoes, the cells are more like underinflated beach balls. The space between these less-than-full cells is taken up mostly by water.

In our tests, we found that the full starch cells of high-starch potatoes are most likely to maintain their integrity and stay separate when mashed, giving the potatoes a delightfully fluffy texture. In addition, the low water content of these potatoes allows them to absorb milk, cream, and/or butter without becoming wet or gummy. Starch cells in lower-starch potatoes, on the other hand, tend to clump when cooked and break more easily, allowing the starch to dissolve into whatever liquid is present. The broken cells and dissolved starch make for gummy mashed potatoes.

Conventional recipes call for boiling large chunks of peeled potatoes. Knowing that the skin can keep potatoes from becoming water-logged when boiled, we wondered what would happen if we peeled the potatoes after boiling.

When we boiled whole russet potatoes with their skins on, then peeled and mashed them, the results were fantastic. The mashed potatoes had a stronger potato flavor and the texture was smoother. By comparison, potatoes cooked the conventional way (peeled and cut into chunks) were watery tasting and a bit grainy.

Potatoes boiled with their skins on were also much drier after ricing or mashing. As a result, they could absorb much more dairy and butter than conventionally cooked potatoes. The result is the richest, most delicious mashed potatoes ever. While it is a bit of a pain to peel hot boiled potatoes, we think the results justify this minor inconvenience.

We prefer to force cooked potatoes through a food mill, which turns the potatoes into fine, thin shreds. With the potatoes already mashed, you can blend in milk and butter with a rubber spatula, which is gentle on those starch cells and therefore helps ensure consistently fluffy mashed potatoes. While a ricer works just as well as a food mill, it is less convenient; the container that holds the potatoes is fairly small, so you need to cut the hot potatoes in half.

The more traditional mashers are usually of two types: a disk with large holes in it or a curvy wire loop. We found the disk to be more efficient for reducing both mashing time and the number of lumps in the finished product. (Potatoes mashed in this way, however, will never be silky, as are those put through a food mill or ricer.) If you choose a masher, don't use a spatula to blend in the other ingredients, as recommended with the food mill and ricer, but blend and mash at the same time to minimize stickiness.

Many recipes call for heating milk before adding it, justifying this by saying that cold milk makes mashed potatoes sticky. Our repeated experiments have demonstrated that this is not true. Cold milk does cool the potatoes, which you really don't want. Our choice is to use warm milk, but only because it keeps the potatoes up to temperature. While you can certainly use milk to make mashed potatoes, our tasters preferred versions made with half-and-half, which gives mashed potatoes a richer mouthfeel and flavor. If you insist on using milk, whole milk is superior to low-fat milk.