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Melt butter, add flour, make a white roux, allow to cool
Make an onion cloute by studding the bay leaf into the onion with the cloves
Place the onion cloute into the milk and heat to just below boiling
Strain the milk through a fine strainer; add 50ml to the roux.
Beat out any lumps, replace roux on heat and bring to the boil
Gradually add the rest of the milk in stages, allowing the mix to boil after each addition ,
and beating out any lumps that form with a wooden spoon before adding any more milk.
Check seasoning, and adjust as needed. Simmer the sauce over very low heat for 20 minutes
to cook out the flour, stirring frequently to prevent burning. Strain the sauce into a clean
container, cover with a buttered cartouche to prevent a skin forming.