How to prepare pierogies?
For dough 3 cups all-purpose flour plus additional for kneading 1 cup water 1 large egg 2 teaspoons vegetable oil 1 teaspoon salt For potato filling 1 1/2 lb russet (baking) potatoes 6 oz coarsely grated extra-sharp white Cheddar (2 1/4 cups) 1/4 teaspoon salt 1/4 teaspoon black pepper 1/8 teaspoon ground nutmeg For onion topping 1 medium onion, halved lengthwise and thinly sliced crosswise 1 stick (1/2 cup) unsalted butter Special equipment: a 2 1/2-inch round cookie cutter Accompaniment: sour cream Make dough: Put flour in a large shallow bowl and make a well in center. Add water, egg, oil, and salt to well and carefully beat together with a fork without incorporating flour. Continue stirring with a wooden spoon, gradually incorporating flour, until a soft dough forms. Transfer dough to a lightly floured surface and knead, dusting with flour as needed to keep dough from sticking, until smooth and elastic, about 8 minutes (dough will be very soft). Invert a bowl over dough and let sta
