Preheat oven to 400°.
In a small bowl, combine the crème fraîche with lemon juice and 2 tablespoons of freshly chopped chives. Season to taste with salt and pepper.
Wash, peel, and dry off the potatoes. Poke them on all sides with a knife. Wrap each of them with a small piece of butter, in foil and place them on a rack in the middle of oven. Place a baking pan under the potatoes to catch any dripping butter. Bake the potatoes for 45 to 60 minutes, until a knife can be easily inserted into them. Remove them from oven. Use caution, as they will be hot.
Let the potatoes cool off for a few minutes. Unwrap them, cut a large X in their tops, and push the sides apart to open. Generously fill the opening with chive sauce and sprinkle with chopped chives. Serve immediately.
