Add the potatoes to a large pot and completely cover with water, add 1 tsp of salt and bring to a boil over medium-high heat. Reduce heat and simmer until tender, about 20 to 25 minutes depending on the size of your cut potatoes. Drain potatoes and set aside.
While the potatoes are cooking melt 4 TBSP of the butter in a medium size pot over medium heat, Add the cabbage and cook until starting to wilt, about 3 to 4 minutes. Pour in the milk and cream, Reduce heat to medium-low, cover the pot and let cook until cabbage is soft, about 10 more minutes.
In a large bowl add the potatoes along with ¼ tsp salt and ¼ tsp pepper, mash the potatoes with a masher until there are no lumps. Fold the cabbage and milk mixture along with the green onions into the mashed potatoes. Make a well in the center of the potato mixture and place the remiaing 2 TBSP of butter in the well. Add additional salt and pepper to taste.
