The Food Lab: Better Home Cooking Through Science

Potato cells contain their own starch, so this really becomes
a question of how to cut the potatoes in order to release just
the right amount. You can grate them on a box grater or in
the food processor, but if you do, you’ll end up rupturing
potato cells, releasing a ton of liquid and starch from inside
them. Then you’re forced to squeeze the shreds dry, and
your rösti will come out starchy and sticky, even with
relatively low-starch potatoes like Yukon Golds.
Much better, though slightly more difficult, is to cut them
on a mandoline. If you have one with extra teeth or blades
(which you should!), it’ll cut the potatoes directly into ⅟₁₆-
inch shreds for you. If you don’t, it’s easy enough to slice
the potatoes into thin planks and then use a knife to get the
matchsticks you need. A sharp mandoline (and a sharp
knife) = fewer ruptured cells = less sticky starch release =
better texture and more potato flavor in each bite. Some
sources recommend rinsing the cut potatoes to rid them
completely of their starch, then adding a measured amount
of pure potato starch to them before cooking, but I find the
results unsatisfactory. Rinsed potatoes don’t soften properly
when cooked, and you end up with rösti with al dente bits of
crunchy potato inside.
The other key to great rösti is to parcook the potatoes
before frying them. Why? Well, anybody who’s worked the
French fry station at a restaurant knows that potatoes begin
to oxidize as soon as you cut them. Over the course of
fifteen minutes or so, a cut potato will go from being pale
white to reddish brown, and eventually to black. You don’t
want your potatoes to be black. Storing sliced potatoes in
water will prevent this from happening (or at least slow it