1. Begin by making the crust. In a large bowl, combine the flour, sugar, and salt. Cut in the cold butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs with some pea-sized pieces.
2. Add the egg yolk and cold water, mixing gently until the dough just comes together. If it feels dry, add a splash more water, but be careful not to overwork it. Wrap the dough in plastic wrap and chill in the fridge for at least 30 minutes.
3. While the dough chills, preheat your oven to 350°F (175°C). Toast the walnuts on a baking sheet for about 8 minutes, stirring halfway through, until fragrant and lightly browned. Set aside to cool.
4. Roll out the chilled dough on a lightly floured surface to about 12 inches in diameter. Gently place it into a 9-inch pie dish, trimming any excess edges and crimping the rim as you like. Chill again for 10 minutes to prevent shrinking.
5. Line the crust with parchment paper and fill with pie weights or dried beans. Blind bake for 15 minutes, then remove weights and paper, and bake for another 5 minutes until the crust is just starting to turn golden.
6. In a medium bowl, whisk together the maple syrup, eggs, brown sugar, melted butter, vanilla, and salt until smooth and well combined.
7. Scatter the toasted walnuts evenly over the partially baked crust. Pour the maple filling over the nuts, spreading gently to level.
8. Bake the pie for 45-50 minutes, until the filling is set around the edges but still slightly wobbly in the center. The filling will firm up as it cools.
9. Allow the pie to cool completely on a wire rack before serving. This resting time is key—it lets the flavors meld and the filling thicken to that perfect sliceable consistency.

One thing Mama Lu always insisted on was patience—whether letting biscuit dough rest or pie filling cool. It’s the waiting that turns good into unforgettable.