300mlmilkmake sure it's cold, 400 ml for a fairly liquid sauce
nutmeg
salt
pepper
Instructions
Gently melt the butter in a saucepan.
Add flour and vigurously well with a whisk or a wooden spatula, you will get what is called a roux.
Pour the cold milk little by little. Whisking constantly to dissolve.
Bring to a boil, stirring constantly, otherwise it will attach to the bottom of the pan. At the first broth lower the heat and cook for 4 to 5 minutes.
Check the consistency of the sauce, it is perfect when the trace remains visible when you pass your finger on the spatula (see photos)
Season with salt, pepper and nutmeg.
Notes
For a fairly liquid béchamelsauce, if you want to use it for gratin casserole for example, add more milk until the desired consistency.