1. Heat oven to 350 degree F. For the crust, process flour, confectioners sugar, and salt in food processor to blend. Add butter and pulse until mixture is the texture of fine meal. Beat egg yolk and vanilla with a fork in a cup. Drizzle over flour mixture. Pulse just until dough begins to hold together. With floured fingers, press dough evenly in bottom and up the side of a 9-1/2-inch tart pan with removable bottom. Prick bottom of tart shell with a fork; freeze 15 minutes. Bake 22 to 23 minutes or until golden brown. Cool on wire rack while making filling. (Leave oven on.)
2. For the filling, heat the 1 cup cream over medium heat in small saucepan until hot. Meanwhile, pulse 8 ounces chocolate in clean bowl of food processor until chopped. With motor on, pour hot cream through feed tube and process until chocolate melts. Add egg and process until blended.
3. Pour filling into crust. Bake 17 to 20 minutes or until filling is set but still jiggly in center (it will continue to set as it cools). Cool tart in pan on wire rack. Remove side of pan. Top with a dollop of whipped cream and garnish with chocolate shavings and mint sprigs, if desired. Serve warm or at room temperature. Makes 12 servings.