- 3/4 cup pure maple syrup (preferably Grade B)
- 1/2 cup (packed) golden brown sugar
- 1/2 cup light corn syrup
- 1/4 teaspoon salt
- 2 tablespoons bourbon
- 1/4 cup (1/2 stick) unsalted butter, cut into 1/2-inch cubes
- Nonstick vegetable oil spray
- 1 refrigerated pie crust (half of 15-ounce package)
- 1 large egg white, lightly beaten to loosen
- 1 cup hazelnuts, husked, coarsely chopped (about 5 ounces)
- 3 large eggs
- 1 teaspoon vanilla extract
- Bring maple syrup, brown sugar, corn syrup, and salt to boil in medium saucepan over medium heat, stirring until sugar dissolves. Continue boiling 1 minute, reducing heat as needed to prevent mixture from boiling over. Remove pan from heat. Add bourbon, then butter; whisk until butter melts. Let cool to lukewarm, whisking occasionally, about 20 minutes.
- Preheat oven to 350°F. Spray 9-inch-diameter glass pie dish with nonstick spray. Unroll pie crust. Line dish with crust. Crimp edges decoratively. Brush crust with enough egg white to coat. Scatter hazelnuts over. Whisk eggs and vanilla extract in medium bowl until blended. Whisk cooled maple-sugar mixture into egg mixture. Pour mixture over hazelnuts in crust. Bake pie until filling is set and slightly puffed, about 50 minutes. Cool completely on rack. DO AHEAD: Can be made 1 day ahead. Cover and keep at room temperature.