Melt the butter in a saucepan and stir in the sifted flour;
Stir well with a whisk until you have a sticky yellowish paste;
Cook it gently for a couple of minutes until thick;
Remove the pan from the heat and pour the hot milk into the mixture, a little at a time;
Stir well to eliminate any clumps until a smooth white cream forms;
Put the pan over medium-low heat and bring to a boil;
Add salt, pepper, and nutmeg;
Cook until it thickens. Just be careful not to overcook it; otherwise, it will get too thick.