Boil pasta in salted boiling water.
Melt the butter in a large saucepan over medium heat. When it starts to foam, add flour. After 3 minutes, add pepper. Stir for a minute. Then pour in a glass of milk and beat until smooth. Pour in the remaining milk, beat again. Bring to a boil over low heat.
Add nutmeg and salt to the mixture. Stir frequently. Turn off the gas and add two thirds of the cheese. Mix well.
Place pasta in saucepan with cheese sauce and stir.
Grease a mold and fill with cheese pasta. Sprinkle the remaining cheese on top and put in an oven preheated to 200 ° C for 15 minutes.