Makes two 8-inch galettes

To make the dough by hand: stir the sour cream and ice water together in a small bowl and set aside. Put the flour, cornmeal, sugar, and salt in a large bowl and stir with a fork to mix. Drop the butter pieces into the bowl, tossing them once or twice just to coat them with flour. With a pastry blender, work the butter into the flour, until the butter pieces are no larger than small peas. Smaller pieces will make the dough tender, larger ones will make it flaky.

Sprinkle the sour cream mixture over the dough, 1 tablespoon at a time, tossing with a fork to evenly distribute it. After you have added all of the sour cream, the dough should be moist enough to stick together when pressed (if not, add cold water 1 teaspoon at a time until you have a soft malleable dough).

To make the dough with a food processor: combine ingredients in the work bowl of your food processor fitted with the metal blade, pulse to combine. Drop butter in and pulse 8-10 times, until butter pieces are pea sized or smaller. With the machine running, add the sour cream mixture and process just until the dough forms moist soft curds.)

Turn the dough out of the bowl. Divide it in half. Press each half into a disk. Wrap each disk in plastic, and refrigerate for at least 2 hours.