In a small bowl, dissolve the cornstarch in coconut water and set aside. In a medium saucepan over low to medium heat, combine the all-purpose cream and sugar. Stir constantly until the sugar has completely melted and the mixture begins to simmer gently. Add the young coconut meat and continue stirring.

Slowly pour in the cornstarch mixture while stirring continuously to avoid lumps. Cook for 3 to 5 minutes or until the filling thickens to a smooth, almost paste-like consistency. Remove from heat and allow the mixture to cool fully before using.

In a large mixing bowl, sift together flour and salt. Add the chilled lard and, using a knife or pastry cutter, cut it into the flour until the mixture resembles coarse crumbs or small peas. Avoid overmixing, as this can make the crust tough.

Mix lemon juice or vinegar into the cold water. Gradually sprinkle this liquid into the flour mixture while tossing gently with a fork until the dough just comes together to form a ball. If possible, refrigerate the dough for easier handling. Divide it into two equal portions—one for the base and the other for the top crust.

On a lightly floured surface, roll out one portion of the dough thinly to fit a 28x4 cm pie pan, leaving about an inch of overhang. Carefully fold the rolled dough in half, then into a quarter, and position it over the pie plate so that the pointed edge aligns with the center. Unfold and ease the dough to fit snugly against the bottom and sides without stretching. Trim any excess to leave a 1-inch edge, fold it under, and gently press to seal. Crimp if desired. Chill for 30 minutes to an hour.

Roll out the second half of the dough into a circle matching the size of the pie pan’s top (about 28 cm). Place it on parchment paper, roll it up loosely, and refrigerate until ready to assemble.

Preheat the oven to 425°F (220°C). Retrieve the prepared crust and spoon in the cooled coconut filling, spreading it evenly. Unroll the chilled top crust over the filling. Trim any excess and press the edges together to seal tightly. Use a fork to prick a few holes across the top crust—this allows steam to escape during baking.

Bake the pie for 10 minutes at 425°F. While it bakes, whisk together the egg and milk to make the egg wash. Remove the pie from the oven and brush the top with the egg wash for a glossy golden finish. Reduce the oven temperature to 350°F (175°C) and continue baking for another 30 to 40 minutes, or until the crust is golden brown.

Allow the pie to cool completely to let the filling set before slicing. Serve warm or chilled for the best flavor and texture.