Mashed potatoes with cabbage

6 medium potatoes1/2 small head green cabbage, shredded6 scallions (with tops), chopped1/4 cup water1/8 teaspoon salt1/3 to 1/2 cup milk1/4 cup butter or margarine, softened1 teaspoon saltDash of pepperButter or margarineHeat 1 inch salted water to boiling. Add potatoes. Heat to boiling; reduce heat. Cover and cook until tender, 30 to 35 minutes; drain.Heat cabbage, scallions, water and 1/8 teaspoon salt to boiling; reduce heat. Cover and simmer until crisp-tender, 5 to 10 minutes; drain.Mash potatoes until no lumps remain. Beat in milk in small amounts. Add 1/4 cup butter, 1 teaspoon salt and the pepper; beat until potatoes are light and fluffy. Stir in cabbage and scallions; dot with butter or margarine.