Fill a saucepan, fitted with a steamer basket, 3 inches high with water. Add potatoes, cover, and steam until tender, about 15 minutes. Meanwhile, lightly flour a baking sheet and set aside.
Remove potatoes from steamer basket. Pass them through a ricer or food mill into a medium bowl. Sprinkle with 3/4 cup flour, and add the egg and egg yolk. Sprinkle with nutmeg and salt. Stir mixture with a fork to combine well. Turn dough out onto a lightly floured surface, knead until smooth (1 to 2 minutes), adding more flour as necessary if dough is too sticky, 1 tablespoon at a time.
Divide dough into 4 to 6 pieces. Roll each piece into a long rope about 3/4 inch thick. Cut ropes crosswise into 1-inch pieces. Set aside on the floured baking sheet until ready to cook.