HEAT oil in Dutch oven on medium heat. Add leeks; cook 5 min. or until tender, stirring occasionally. Add potatoes, water, salt and pepper; cover. Bring to boil; simmer on medium-low heat 15 to 20 min. or until potatoes are tender. Cool 10 min.
BLEND leek mixture, in batches, in blender until smooth. Return to pan. Add cream cheese, a few cubes at a time; cook on medium heat until cream cheese is completely melted and mixture is well blended, stirring constantly.
ADD milk; cook 2 to 3 min. or until heated through, stirring occasionally. Top with chives.