4 small russet potatoes or 2 sweet potatoes (22 to 24 ounces total), peeled, cut into 1/2-inch pieces 1 large egg 2 tablespoons whipping cream 1 1/4 teaspoons salt 1/8 teaspoon ground nutmeg 1 1/2 cups (about) all purpose flour
Cook potatoes until tender, about 12 minutes. Working in batches, press warm potatoes through ricer into a large bowl (or place warm potatoes in large bowl and mash finely with potato masher). Cool until lukewarm, about 10 minutes. Add egg, cream, salt, and nutmeg and blend well. Add 1 1/2 cups flour and mix until soft and slightly sticky dough forms, adding more flour by tablespoonfuls if too moist.
Turn dough out onto lightly floured work surface. Divide into 6 equal portions. Gently roll 1 dough portion between hands and work surface to 3/4-inch-thick rope about 20 inches long. Cut into 3/4-inch-long pieces.
Roll each piece over wires of slender whisk or dinner fork to make grooves in gnocchi. Arrange gnocchi in single layer on floured baking sheet. Repeat with remaining 5 dough portions.
Cook gnocchi in three batches in a large pot of boiling generously salted water until gnocchi rise to top and are cooked through and tender, about 5 minutes (check at 4 minutes). Using large strainer or slotted spoon, transfer gnocchi to serving dish.