300 ml semi-skimmed milk
15 gr. flour
1 onion slice
1 mace blade
1 bay leaf
15 gr. butter
Pour the milk into a saucepan; add the onion slice, peppercorns, mace and bay leaf.
Bring almost to the boil; remove from the heat and cover.
Then leave to infuse for 30 minutes and strain.
Meanwhile melt the butter in a saucepan, stir in the flour and cook, stirring, for 1 minute until cooked to obtain a roux.
Season with salt, pepper and nutmeg to taste.
Put it all together and cook until the sauce is thickened and smooth, stir constantly and simmer for 2 minutes.