Prepare your ingridinets.
In a saucepan, over a low-to-medium heat, bring the milk to a simmer. Whisk the milk from time to time to prevent a skin from forming.
Melt the butter in a saucepan over low-to-medium heat. Add all the flour and stir continuously for 1 to 3 minutes. Be sure not to brown the roux. After around 3 minutes, remove the pan from the heat and let it cool slightly.
Gradually add the warm milk while whisking constantly to prevent lumps. After adding 3–4ladles of milk and incorporating them into the sauce, you can add the remaining milk at once.Cook the sauce gently for around 30-40 minutes , skimming off the skin that will form. Cook the sauce gently for around 30-40 minutes , skimming off the skin that will form.
Season to taste with salt, white pepper, and freshly grated nutmeg.
Enjoy you sauce Béchamel .