In a large bowl, combine the flowers, mascarpone, egg, Parmigiano-Reggiano, salt and nutmeg. Mix well to form a dense but not overly-stiff mixture. Set aside.
Divide the prepared pasta dough into 3 balls of equal size. Roll each ball out to the thinnest setting on a pasta rolling machine. Cut each sheet into 5-inch squares. Place a generous tablespoon of the cheese and flower mixture in the center of each square and fold each square, corner to corner, to form a triangle. Fold the other 2 corners together to form the tortello. Place the tortelli on a sheet tray dusted with flour until ready to cook.
Bring 6 quarts of water to a boil and add 2 tablespoons salt.
In a 14 to 16-inch saute pan, heat the butter until it foams and subsides.
Meanwhile, cook the tortelli in the boiling water for 2 minutes. Drain the pasta, reserving the cooking water, and add to pasta to the pan with the butter. Add a splash of the pasta water and the sage leaves and toss over high heat 1 minute to coat and emulsify. Divide the pasta evenly among 4 warmed pasta bowls, grate Parmigiano-Reggiano over, and serve immediately.
Mound 3 1/2 cups of the flour in the center of a large wooden cutting board. Make a well in the middle of the flour and add the eggs and the olive oil. Using a fork, beat together the eggs and oil and begin to incorporate the flour, starting with the inner rim of the well.
As you expand the well, keep pushing the flour up from the base of the mound to retain the well shape. The dough will come together when half of the flour is incorporated.
Start kneading the dough with both hands, using the palms of your hands. Once you have a cohesive mass, remove the dough from the board and scrape up and discard any leftover bits. Lightly reflour the board and continue kneading for 6 more minutes. The dough should be elastic and a little sticky. Wrap the dough in plastic and allow to rest for 30 minutes at room temperature. Roll or shape as desired.
Recipe copyright 2000, Mario Batali. All Rights Reserved.