Cut the potatoes into large chunks, and place in a large pot of salted water. Bring to the boil, and cook until the potatoes and soft when tested with a knife. Drain well.
In a small pot, combine the butter and milk or cream & melt over a medium heat.
Mash the potatoes, slowly incorporating the milk and butter mixture. Season to taste, then fold through the Tatua Mascarpone.
Transfer to a serving bowl and finish with grated parmesan and freshly chopped chives.