-4 med or 2 larges leeks, thoroughly rinsed, bottoms trimmed, white and green parts chopped into thin rings. Be sure to separate the outer layers and rinse as you reach the joint of white and green where dirt hides.
-5 med. to large white or yellow potatoes, boiled and thoroughly mashed
-4 tbsp. Butter
Melt butter in soup pot at med. temp. Sautée leeks slowly, turning over frequently to cook evenly throughout, without browning, until green parts are tender. Stir-in 3 tbsp flower with a wooden spoon to make a paste adding one tbsp more at a time until the paste is a bit stiff, but still able to bubble. Stir continuously allowing paste to cook for a couple of more minutes without turning brown. Stir-in just enough water to dissolve the paste, continuing to stir, being sure to press-out any lumps and prevent the cream sauce from sticking to the bottom of the skillet, form lumps or burn, reducing the heat if necessary. Remove from heat when sauce is thick enough so that a track behind the spoon when dragged across the skillet doesn't fill back in Instantly.
Gradually stir milk into the mashed potatoes to get a soupy but substantial purée. Stir the puree into creamed leeks. Add milk as needed to reach desired cream soup viscosity being careful not to over-dilute flavor. Adjust salt.