1. Line a 9-inch pie plate with crust, decorate edge and place in freezer until ready to fill.
2. Heat oven to 350 degrees F with rack in the lower third. Bring maple syrup, brown sugar, corn syrup and salt to a boil in saucepan over medium heat, stirring until sugar dissolves. Continue boiling 1 min, reducing heat as needed to prevent mixture from boiling over. Remove pan from heat. Add bourbon and butter and stir until butter melts. Let cool to lukewarm.
3. Spread hazelnuts in prepared crust in pie plate. Beat together eggs and vanilla, whisk in cooled maple mixture and pour over hazelnuts. Bake pie until filling is set and slightly puffed, about 1 hr; cover crust with foil for the last 20 min to prevent overbrowning. Cool completely.
4. Toss extra hazelnuts with a little metallic dust for garnish. Store pie, covered, for up to a day. Makes 8 servings.