Heat the milk but do not bring to a boil.
Melt the butter over a very low heat, see that it does not boil.
When the butter melt, add to the flour and mix well with a whisk, constantly stirring, keep on fire for several minutes.
Then pour in a third of warm milk and mix well again. After pour the rest of the milk and cook constantly stirring until thickened.
When the sauce thickens, remove it from the heat, add pepper and salt to taste.
Transfer the sauce to a bowl and cover with cling film to touch the surface of the sauce.
The sauce is ready.
Bechamel lasagna sauce is very tender and delicious, it is very simple and fairly quick to cook. This is one of the most popular sauces, it is also called simply white sauce. Such a sauce can be stored in the refrigerator in an airtight container for about 3-5 days. The amount of sauce is designed for large six-layer lasagna. Before cooking, the sauce needs to be heated and only then used.