What makes these mashed potatoes taste homemade is the perfect imperfection of the potatoes, with strategic lumps and skin. Also, skip the yukons and go for the traditional russets, just like Grandmama did.
Peel the potatoes, leaving some of the skin. Cover potatoes in 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, leaving some lumps and skin on the potatoes. 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. Finish with the remaining butter and cream, and salt with the fleur de sel to taste.
Potatoes may be made up to 2 hours ahead of time and reheated when you are ready to feast.