1 In A Large (6-Quart) Pot, Heat The Butter On Medium High Heat Until It Melts And Foams Up. Continue To Heat Until The Foam Subsides A Little And The Butter Just Begins To Brown. 2 Immediately Toss In The Sliced Leeks And Onions. Stir To Coat With The Butter. Cook For Several Minutes, Reducing The Heat To Medium If Necessary, Until The Leeks And Onions Are Translucent And Wilted. 3 Add The Chopped Potatoes, Salt, And Water Or Stock. Bring To A Boil, Reduce To A Simmer. Cook, Partially Covered For 30-40 Minutes, Until The Potatoes Are Completely Cooked Through. Remove From Heat. 4 Pur