Place the potatoes and whole garlic cloves in a pot and cover with cold water. Add salt and bring to a boil. Cook potatoes and garlic for about 15-20 minutes or until tender. Drain.
While the potatoes are boiling, cook bacon in a large pan until crisp. Reserve drippings and crumble bacon, set aside.
Add 1 tablespoon of the butter to the bacon drippings and saute the green onions, leeks and cabbage over medium heat until onions are translucent and cabbage is wilted, about 4 minutes. Remove from heat.
Mash potatoes, adding cream and ¼ cup butter until smooth. Add salt and pepper to taste. Fold in cabbage, onion and leek mixture and top with crumbled bacon and additional melted butter if desired.