How to cook
The leeks are cleaned and finely chopped. Stew them in olive oil. In another pan, heat the butter and add the flour to it.
Once the butter is absorbed into the flour, gradually add the milk and boil the mixture until a thick sauce is obtained. The sauce is added to the leeks.
Beat the egg along with the salt and white pepper and add them to the mixture. Mix well and leave the mixture for 40 minutes in the refrigerator.