500 gr milk
50 gr butter
50 gr flour
salt, pepper and nutmeg
Melt the butter in a saucepan and as it melts, add the flour and, over a low heat and using a small wooden spoon, stir to make a smooth paste. Now begin adding the milk a little at a time. Once the milk is incorporated, add the next amount and continue incorporating each bit of liquid before you add the next.
Now turn the heat down to its lowest setting and let the sauce cook 10 minutes, whisking from time to time. Taste and season with salt, nut meg and freshly milled black pepper.