In a large saucepan cook potatoes, covered, in a small amount of boiling salted water for 20 to 25 minutes or until tender. Drain.
In a medium saucepan, cook cabbage, uncovered, in a small amount of boiling salted water for 2 minutes. Cover and cook for 6 to 8 minutes more or until tender. Drain.
Mash potatoes. Stir in milk, onions, and parsley. Season to taste with salt and pepper. Add butter or margarine and drained cabbage. Stir until butter or margarine is melted and mixture is combined. Makes 12 side-dish servings.