Melt the butter in a saucepan and add the flour, stirring with a wooden spoon. Add the milk gradually, stirring rapidly with whisk. When blended and smooth, add the garlic, pepper, nutmeg. Add enough milk to obtain the consistency you require. Simmer gently for 5 minutes stirring the bottom regularly to ensure it doesn't burn.
Do not reboil after adding egg yolk.
Forms the base for many white sauces eg.