Preheat the oven to 375 degrees. In a small saucepan, bring the sugar, maple syrup and butter to a simmer, stirring until the sugar dissolves. Remove from the heat; let cool to room temperature.
In a large bowl, whisk together the eggs, lemon juice, vanilla and salt. Stir in the cooled syrup mixture, then the nuts. Place the pie shell on a baking sheet and pour in the filling. Bake for 10 minutes. reduce the oven temperature to 325 degrees and bake until the crust is golden-brown and the filling is set, about 50 minutes. Let cool on a rack.
In a small microwavable bowl, melt the chocolate chips at medium power (50%) for 30 seconds. stir, then continue microwaving in 10-second intervals, stirring in between, until chocolate is smooth. Dip the tines of a fork into the melted chocolate and drizzle over the pie. let stand until the chocolate sets, about 20 minutes.