Preheat the oven to 425 degrees F.
Rinse the duck cavity with the grappa. Place the herbs inside the body, season the inside with salt and pepper and truss the duck with butcher's twine.
Cover the bottom of a roasting pan with a 1/2-inch layer of salt. Place the duck atop the salt, beat the egg white to a light froth and mix 1 1/2 pounds of kosher salt to form a moist paste. Cover the duck completely with the salt mixture and roast in the oven for 1 1/2 hours. Remove and allow to rest 10 minutes to allow the juices to settle. Carefully remove the salt from the bird and brush off with a paint brush. Remove the skin and then carve the bird in the traditional way. Drizzle with saba and serve with wilted greens on the side.