Prep: 15 minutes; Cook: 58 minutes; Chill: 1 hour.
Preheat oven to 375°. Working with prepared dough, press down edges with floured fork tines, leaving 1-inch between crimping. Freeze 10 minutes or until firm.
Line bottom of dough with foil; arrange pie weights on foil. Bake in middle of oven 20 minutes or until set. Remove weights and foil; brush edges with egg white, and sprinkle with turbinado sugar. Return to oven; bake 8-10 minutes more. Transfer to a wire rack; let cool.
Turn oven down to 325°. Bring milk, granulated sugar, and salt to a simmer in a pan over medium-high heat. Remove from heat; stir in chocolate, and let stand 5 minutes. Whisk until melted. Whisk in sour cream, then whisk in egg yolks and vanilla.
Pour filling into crust, and smooth top with a spatula. Bake in middle of oven 25-35 minutes or until just set. Transfer to a wire rack to cool, and chill until firm, at least 1 hour or up to overnight. Top with toasted hazelnuts; slice and serve.