Place the potatoes in a large saucepan with enough lightly salted water to cover. Bring to a boil over medium-high heat. Reduce the heat and simmer for 15 to 20 minutes or until fork tender. Drain well, ensuring excess water is removed. Add 4 tablespoons of butter and cream. Cover the pot and let the butter melt.

Meanwhile, melt 2 tablespoons of butter in a large skillet over medium heat. Add the chopped onion and cook until tender. Add cabbage and cook until tender and lightly browned on the edges, about 7-8 minutes.

Mash the potatoes with a potato masher and gently stir in the cabbage mixture and half of the chopped bacon. Season with kosher salt and fresh ground black pepper to taste. Top with the remaining chopped bacon. Transfer to a serving bowl. Cut the remaining tablespoon of butter into pats. Make a small well on top and add the remaining butter.