Put the milk, onion, bay leaf, cloves and peppercorns into a medium-sized saucepan, and heat until it’s just about boiling.
Turn off the heat and leave the mixture to stand for 25 minutes, then strain it through a sieve (or take the bits out with a slotted spoon, and save them for adding to a soup!).
Melt the butter in a non-stick pan, and stir in the flour – this will turn into a paste (known as a roux).
Cook this gently over a low heat for 3-4 minutes – and don’t stop stirring!
Now add some of the strained milk, a bit (a short pour) at a time. Keep stirring as you add it in, and it’ll slowly turn into a thick sauce.
Simmer the sauce gently for 10-15 minutes.
Taste it (carefully – we’ve burnt our tongues more than once!), add the nutmeg and some salt and black pepper.
Add 100g of cheddar at step 6 to make a rich, cheesy white sauce (and pour over cauliflower to make cauliflower cheese).