Boil potatoes for about 40 minutes. Drain and peel.
In a mixing bowl, crush the potatoes with a masher until smooth. Add 1/2 cup of the cheese, 1/2 cup chives, eggs, and nutmeg, and mix well.
Bring 6 quarts water to boil and add 2 tablespoons salt.
Using a pasta roller, roll out the pasta to thinnest setting and cut into 4-inch squares. Place 1 tablespoon potato mixture in center of each square. Fold opposite corners of each square together and press firmly to seal and form a triangle. Bring the opposite points of the triangle together and press firmly to meld. Continue until all the pasta is stuffed and formed into tortelli. Drop pasta into boiling water and cook until tender, about 6 to 7 minutes.
Meanwhile, melt the butter in a 12 to 14-inch saute pan and continue cooking until you begin to see hints of a golden brown color (noisette), appearing in the thinnest liquid of the butter. Add the sage leaves and remove from heat. Add the lemon juice and set aside. Drain the tortelli well, gently pour into saute pan and return to heat. Add the remaining chives and cheese, toss to coat and serve immediately.
Mound 3 cups of flour in the center of a large wooden cutting board. Make a well in the middle of the flour, add the eggs. Using a fork, beat together the eggs and begin to incorporate the flour starting with the inner rim of the well. As you incorporate the eggs, keep pushing the flour up to retain the well shape (do not worry if it looks messy). The dough will come together in a shaggy mass when about half of the flour is incorporated.
Start kneading the dough with both hands, primarily using the palms of your hands. Add more flour, in 1/2-cup increments, if the dough is too sticky. Once the dough is a cohesive mass, remove the dough from the board and scrape up any left over dry bits. Lightly flour the board and continue kneading for 3 more minutes. The dough should be elastic and a little sticky. Continue to knead for another 3 minutes, remembering to dust your board with flour when necessary. Wrap the dough in plastic wrap and set aside for 20 minutes at room temperature. Roll and form as desired.
Note: Do not skip the kneading or resting portion of this recipe, they are essential for a light pasta.
Yield: 1 pound of pasta, about 4 servings
Recipe courtesy of Mario Batali