Place peeled potatoes in a heavy pot and fill the pot with just enough cold water to submerge the potatoes. Heat on medium-low and simmer until a sharp knife can pierce the potato without resistance. The cook times will depend on the size of the potatoes (approximately 40-50 minutes for whole medium potatoes). Check for doneness using a skewer or knife to piece the potato. When done, you shouldn't have any resistance when piercing them through the center.

While the potatoes cook, add butter, cream and milk to a small saucepan and warm over low heat. Be careful not to boil the cream mixture - you want it warm but not boiling.

When potatoes are done, drain and remove the hot potatoes to a large bowl. Using a potato ricer or masher, rice potatoes back into the warm large pot used to cook the potatoes. Add the warm cream and butter mixture, sour cream, white pepper, and salt into the warm pot with the riced potatoes (off the heat).

Mix the riced potatoes with a rubber spatula with the wet ingredients until thoroughly combined. If you need to add anything to thin the mixture out, you can use extra milk or melted butter - gradually adding to achieve the texture you want.

Add the grated Parmesan and fold in with a spatula. Taste for seasoning and add more white pepper or salt and extra cheese and chives (optional) as needed or to your taste. Voilà - serve and enjoy!