Boil potatoes in salted water until done, 15-20 minutes. Drain, add milk, then mash.
Boil cabbage in water until fork tender, 8-12 minutes. Drain.
Cook green onions in 6 tbsp. butter in a large sauce pan. Add the mashed potatoes and cabbage. Mix all ingredients and heat together. Add salt, pepper, and more milk if desired. Serve with last 2 tbsp butter on top.