Place a foil lined baking sheet or stone in the oven and preheat to 375° F degrees.
Prepare a 9-inch unbaked pie crust. Pour the walnuts in the pie crust and set aside.
Melt the butter and set aside to cool slightly. In a medium mixing bowl whisk the eggs until blended. Add the brown sugar, flour, maple syrup, salt, vanilla, cinnamon and nutmeg. Whisk until blended. Add the melted and cooled butter. Whisk together and pour over the walnuts in the unbaked pie crust.
Bake the pie on the preheated baking sheet for 45 minutes or until the pie filling is puffed and set and no longer jiggly.
Cool to room temperature and serve.