Set an oven rack in the bottom third of your oven. Preheat the oven to 375°F.
Set the piecrust on a parchment paper-lined baking sheet. Sprinkle the walnuts in the bottom of your piecrust.
Place the eggs and brown sugar in a large bowl and whisk until very smooth. Whisk in the maple syrup, cream, vanilla and flour until very smooth.
Pour the maple syrup mixture into the piecrust. Bake for 40 to 45 minutes, or until the filling is puffed, looks dry on top, but still jiggles.
Set the pie on a baking rack and cool to room temperature. The filling will set as the pie cools. You could also keep the pie refrigerated, if desired, until ready to serve.