Cook potatoes in boiling water to cover 15 to 20 minutes or until tender; drain. Peel and slice potatoes; set aside.
Melt butter in a skillet over medium heat; add leek, onion, and ham. Sauté 5 to 7 minutes or until leek is tender.
Stir together flour and 2 tablespoons water. Add flour mixture, broth, and pepper to ham mixture. Cook over medium heat, stirring occasionally, until thickened and bubbly. Stir in parsley and next 4 ingredients. Stir in reserved potato. Sprinkle with cheese.