On a lightly floured surface, roll out one disk of piecrust to a 1/8-inch-thick circle, about 13 inches in diameter. Drape dough over a 9-inch pie pan. Transfer pan to refrigerator, and chill 30 minutes.
Heat oven to 425 degrees. Whisk together the egg yolk and cream; set aside.
In a large bowl, toss together the apples, lemon juice, granulated sugar, flour, cinnamon, nutmeg, and salt; place in chilled bottom crust. Dot with butter.
Roll out the remaining disk of piecrust as in step one. Brush the rim of the bottom crust with the egg wash. Place second piece of dough on top, and trim so 1 inch overhangs. Tuck the dough under, and crimp the edges with a fork or your fingers. Transfer pie to the refrigerator, and chill until firm, about 15 minutes.
Remove pie from the refrigerator, brush with the egg wash, and sprinkle generously with sugar. Cut four vents in the top, allowing the steam to escape.
Bake until crust begins to turn light brown, about 25 minutes. Reduce temperature to 350 degrees, and bake until golden brown and the juices are bubbling, 25 to 30 minutes. Transfer to a wire rack to cool. Serve pie with vanilla ice cream, if desired.