Peel the potatoes and cover in a heavy pot with just enough water to fully submerge. Add 6–7 tablespoons of salt and bring to a boil. Immediately lower heat and continue to simmer until potatoes are very tender and fully cooked, about 20–25 minutes. Drain well. 

Peel the potatoes and cover in a heavy pot with just enough water to fully submerge. Add 6–7 tablespoons of salt and bring to a boil. Immediately lower heat and continue to simmer until potatoes are very tender and fully cooked, about 20–25 minutes. Drain well. 

Pass potatoes through a food mill or potato ricer.  Heat milk and cream with about 3 tablespoons of fleur de sel until just simmering. Over low heat, slowly add 1/2 cup milk at a time to the potatoes until absorbed, stirring gently with a spatula. The secret to the potatoes is slow cooking, allowing the milk to absorb, and constant stirring, almost like a risotto. When you have only a half-cup of milk left, add in the butter a quarter stick at a time, alternating with the milk. Stir in the sour cream and the goat cheese.  Finish with the remaining butter and cream and fleur de sel to taste. Potatoes may be made the day before, and reheated at 400 degrees the day of Thanksgiving.  If pre-making the potatoes, do not add the chives.  Snip the chives right before serving on top of the dish.