In a large saucepan, bring cabbage and water to a boil. Reduce heat; cover and simmer for 10-12 minutes or until tender. Drain, reserving cooking liquid. Keep cabbage warm.
Place cooking liquid and potatoes in a large saucepan; add enough additional water to cover the potatoes. Bring to a boil. Reduce heat; cover and cook for 15-17 minutes or until tender. Drain and keep warm.
In a small saucepan, bring milk and onions to a boil; reduce heat and simmer until tender; remove from the heat.
In a large bowl, mash potatoes. Add milk mixture; beat until blended. Beat in the cabbage and season with salt and pepper. Pour into a serving bowl; drizzle with the melted butter, and sprinkle with crumbled bacon and chopped parsley.