Basic White Sauce
Pour the whole milk into a small saucepan and add the slices of carrot, the slices of onion, the sprig of parsley, the sprig of thyme, and the peppercorns. Bring the mixture to the boil, then decrease the heat and simmer for four to five minutes. Remove from the heat and leave to infuse for about 10 minutes.
While the milk infuses, make the roux. Melt the butter in a small saucepan over a low-to-medium heat and add the plain flour. Allow to cook for two minutes, stirring regularly. Set aside.
Strain the milk mixture through a sieve that you've placed over a small saucepan, and bring the milk to the boil. Whisk in the roux, a little at a time, until it is well blended, and leave the sauce to simmer gently for four to five minutes, or until it has thickened to the desired consistency. Season to taste with salt and freshly ground black pepper.
Use as a plain white sauce or add your choice of flavouring or cheese.