Add sugar, water and butter to reduced cider and return pan to high heat. Bring to a simmer, then reduce heat and cook at a gentle simmer until mixture reduces to 1 cup, about 10 minutes. Transfer mixture to a medium, heat-proof mixing bowl and cool to room temperature. It will thicken as it cools.
Separate eggs, and whisk the yolks into the cooled cider mixture. With an electric mixer on high speed, beat egg whites until just firm and fold them into the cider mixture, a third at a time. Make certain all the cider mixture is folded into the whites.
Spoon filling into the prepared pie shell. (Shell will be about 2/3 full when all the filling has been added.) Bake 10 minutes, then reduce heat to 350 degrees. Continue to bake until crust is golden brown and filling has puffed and set and has become dark brown on top, about 25 minutes more.
After 10 or 15 minutes at 350 degrees, check, and if filling and crust are browning too quickly, cover pie with a buttered sheet of foil (buttered side down).
Remove and cool to room temperature. (Pie can be made 5 hours ahead; leave uncovered at room temperature.) To serve, place creme fraiche in a serving bowl, and whisk in 1 to 2 tablespoons cream, half-and-half, or milk to lighten slightly.
Dust pie with confectioners’ sugar. Garnish each slice with a generous dollop of creme fraiche. Makes 8 servings.
Betty Rosbottom is a cooking school director and author of “Big Book of Backyard Cooking” (Chronicle Books).
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