Finely chop half of the onion and cook gently in 50 g of the butter until soft.
Stud the other half with the cloves, pushing them through the bay leaf to anchor it.
Put the milk, nutmeg and studded onion into the pan with the cooked onion and bring it to the boil.
Season then simmer for 30 minutes.
Remove the pan from the heat and leave the milk to infuse for 30