Peel and coarsely chop the potatoes, Butternut squash, sweet potatoes, carrots, parsnips, turnip, and onion. Wash the leeks and cabbage to remove any debris, then chop.
Toss all into a large heavy-bottomed stock pot and then pour in the Ham Hock Stock, add water if need to bring the level up to barely cover the vegetables. Bring to a boil over medium-high heat, then reduce the heat and allow to simmer partially covered till vegetables are tender. About 20 minutes.
Meanwhile, cook the smoked sausage until browned and cooked through.
Drain the vegetables well, then mash, with the butter. Season with salt and pepper.
Serve with sliced smoked sausage and a knob of butter if desired.