1 - Melt butter in a stainless steel saucepan.
2 - Add flour stirring vigorously with a whisk to avoid lumps.
3 - stirring vigorously with a whisk to avoid lumps.
4 - Pour the milk, previously heated, a little at a time and stirring continuously.
5 - Once poured all milk, set to boil and cook 5 minutes, adding a pinch of salt.
6 - Turn off and add half half teaspoon of ground nutmeg and 3 tablespoons of grated parmigiano (or grana)