This sauce is is wonderful in lasagne, baked pasta or gnocchi dishes. This sauce is easy to make, but a word of advice, get all your ingredients ready to hand and make sure your milk is hot, as then sauce will burn quickly if you don't keep an eye on it, and use the right amount of ingredients or it WILL go lumpy. I often add a little less flour and a pinch of grated Parmesan to flavour the sauce.
50g plain flour
500ml hot milk, not boiling
pinch salt and pepper
pinch freshly grated nutmeg
Melt the butter in a pan over a steady low heat. When melted add the flour and stir until you have a smooth paste.
Gradually add your hot milk, a little at a time, stirring constantly, until your sauce begins to thicken, but has no lumps. After about 10 minutes, the sauce should have thickened, take off the heat and add a pinch of grated nutmeg and season with salt and pepper.
* If your sauce goes lumpy, use a hand whisk to beat the lumps out.