1/2 lb prosciutto,
1 cup freshly grated parmesan,
3 eggs,
1 lb spaghetti,
1/2 cup butter, in small pieces.

Cut prosciutto into small pieces.
Beat eggs lightly with a fork and add 1/3 cup of the parmesan. Only use Italian Parmigiano-Reggiano or Grana Padana cheese.
Boil in abundant salt water 1 lb of spaghetti, until "al dente".
Drain, replace in the cooking pan and mix with butter. Then, always mixing, quickly add the egg and cheese mixture.(The egg must cook with residual heat.)
Serve immediately, sprinkling each dish with the balance of the cheese.