Peel and chop the potatoes into equal cubes about 1 inch thick. Keep cut potatoes in a bowl full of cold water to prevent them from going pink.
Place the potatoes into a large pot and pour enough water to cover the potatoes. Add a generous amount of salt and bring to a boil.
Lower the heat slightly and cook potatoes until fork tender- about 20 minutes.
Meanwhile keep the cream warm in a small saucepan over low heat. Make sure it doesn't boil or the milk solids in the cream will curdle.
Drain the potatoes and return them back to the hot pot. Turn the heat down to the lowest setting and allow the residual moisture to dry off.
Using a potato ricer or an electric mixer (or even a whisk!) mash potatoes until uniformly smooth.
Gradually stir in the warm cream, sour cream, melted butter, Dijon mustard and salt. Continue whipping the potatoes until smooth and fluffy. If the mixture looks a bit stiff and dry, add 1/4 cup milk at a time until the desired consistency is reached.
Mix all together and adjust seasonings to taste. Top with pats of room temperature butter and chopped parsley or chives. Enjoy warm!