CUT white portion and 1 inch of light green portion of each leek into thin slices. Melt butter in large skillet on medium heat. Add leeks; cook and stir 5 min. or until crisp-tender. Stir in all remaining ingredients except VELVEETA.
BRING to boil; cover. Simmer on low heat 15 min. or until potatoes are tender.
ADD VELVEETA; cook 5 min. or until VELVEETA is completely melted and mixture is well blended, stirring frequently.