In a medium bowl, whisk together the all-purpose flour, granulated sugar, and pinch of salt.

Add the cold, cubed butter to the dry ingredients. Using a pastry blender, your fingertips, or a food processor, cut the butter into the flour mixture until it resembles coarse crumbs with some pea-sized pieces of butter remaining.

Gradually add the ice water, one tablespoon at a time, mixing gently after each addition until the dough just begins to come together. Be careful not to overmix.

Gather the dough into a ball, flatten it into a disc, wrap it in plastic wrap, and refrigerate for at least 30 minutes. This chilling step is crucial for a tender crust.

Preheat your oven to 375°F (190°C).

On a lightly floured surface, roll out the chilled dough into a circle large enough to fit into a 9-inch pie plate.
Carefully transfer the rolled-out dough to the pie plate. Press it gently into the bottom and up the sides. Trim any excess dough and crimp the edges decoratively.

To prevent the crust from puffing up too much, you can prick the bottom with a fork several times. For an even more foolproof crust, you can blind bake it. To do this, line the unbaked crust with parchment paper and fill it with pie weights or dried beans. Bake for 15 minutes, then remove the parchment paper and weights and bake for another 5-7 minutes until lightly golden. Let the crust cool slightly while you prepare the filling.

In a large bowl, whisk together the sweetened condensed milk and regular milk until well combined.

In a separate small bowl, lightly whisk the egg yolks.

Gradually temper the egg yolks by slowly drizzling about half a cup of the warm milk mixture into the egg yolks while whisking constantly. This process prevents the eggs from scrambling.

Pour the tempered egg yolk mixture back into the remaining milk mixture in the large bowl.

Add the vanilla extract to the filling.

If using, stir in the chopped pecans or walnuts at this stage.

Pour the prepared filling into the pre-baked (or unbaked, if you skipped blind baking) pie crust.

Carefully place the pie on a baking sheet to catch any potential drips during baking.

Bake in the preheated oven for 35-45 minutes, or until the filling is set and a knife inserted near the center comes out clean. The top should be lightly golden brown.

Remove the pie from the oven and let it cool completely on a wire rack. This is crucial for the filling to set properly. This may take several hours.

Once completely cooled, you can chill the pie in the refrigerator for at least 2 hours before serving for the best texture.