Heat the milk in a saucepan, over a medium heat, until it comes to a simmer.
Turn off the heat and transfer the milk to a jug.
Add the butter to the pan and heat until melted then tip in the flour and stir to combine.
Keep stirring for a minute.
Now add about a quarter of the milk to the pan, stirring all the time until it thickens.
Stir in the rest of the milk and cook for a further minute.
Season to taste and add nutmeg if you like.
Notes
Disclaimer:The nutritional information provided is approximate and is calculated using online tools. Information can vary depending on various factors, but we have endeavoured to be as accurate as possible.Top tips
If you are making this sauce to be served as it is, such as for lasagne, then you can add extra flavours to the milk, when heating. Try a bay leaf and a few peppercorns and leave to infuse in the warm milk.
You can skip straight to making the roux first, to avoid needing a jug for the milk, but you will need to stir the cold milk for longer while it thickens.