Published November 1, 2009.
After weeks of testing, we discovered the secrets to the crispiest, creamiest roasted potatoes ever: the right spud, the right shape, and—surprisingly—a not-so-delicate touch.
Almost any vegetable will come out edible, if not tasty, if roasted with plenty of salt and oil. The problem is that foolproof techniques for consistently good crisp roasted potatoes are few and far between.
We set out to achieve potatoes that were crisp on the outside and silky-smooth on the inside.
Our research revealed that for a potato to brown and crisp, two things need to happen, both of which depend on moisture. First, starch granules in the potatoes must absorb water and swell, releasing some of their amylose, a water-soluble type of starch. Second, some of the amylose must break down into glucose (i.e. sugar). Once the moisture evaporates on the surface of the potato, the amylose hardens into a shell, yielding crispness, and the glucose darkens, yielding an appealing brown color. In the dry heat of the oven, this is a lengthy process because the starch granules swell slowly, releasing little amylose. In contrast, parboiled potatoes are swimming in the requisite moist heat, releasing lots of amylose on the surface of the potato. By the time parcooked spuds get transferred to the oven, they are ready to begin browning and crisping almost immediately.
We knew that parcooking was key, but was boiling, the traditional cooking method, the best way to go? We found that drawing out the starch and sugar quickly and washing away the excess was the magic formula to a crisp exterior, and the key to doing this was a slightly gentler parsimmering (bringing to a boil, then immediately reducing the heat so that the vigorous action of boiling wouldn’t wash away too much starch). We also achieved even browning by cutting the potatoes into rounds—with only two surfaces, we only had to flip them once.
We still needed to up the crispness and the creaminess of our potatoes. We observed that the parcooking step was doing more than just jump-starting the surface starch; it was also speeding up evaporation by creating a rough surface. A rougher surface offers more escape routes for moisture than the flat surface of a raw potato, and the damaged exterior cells surrender their moisture more readily than intact cells. So why not rough up the surface even more? We tossed the potatoes vigorously with olive oil and salt, forming a thick layer resembling mashed potatoes on the exterior. Once roasted, the spuds were crisper than ever—and nicely seasoned, to boot.
As for potato choice, we settled on Yukon golds. They crisped up perfectly, and their moderate moisture kept the interiors creamy.
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