Preheat oven to 425°F (220°C). In a food processor, combine flour, sugar, and salt. Add chilled butter and pulse until mixture resembles coarse crumbs.

Slowly drizzle in ice water until dough begins to hold together. Shape into a ball, wrap in plastic wrap, and refrigerate for 30 minutes.

On a floured surface, roll dough into a circle 2 inches larger than your pie pan. Transfer to the pan, trim excess, and crimp edges.

Line crust with parchment paper and fill with pie weights or beans. Bake 15 minutes. Remove weights, brush with egg wash, and bake another 10–15 minutes until golden. Cool completely.

For the filling: Heat milk with vanilla until almost simmering. In a bowl, whisk eggs, yolks, sugar, salt, and cornstarch until smooth. Gradually add warm milk while whisking to temper the eggs.

Return to pot and cook over medium heat, whisking constantly until thickened. Remove from heat and stir in butter. Cool to room temperature.

Pour filling into baked crust, smooth top, and cover with plastic wrap. Chill for at least 4 hours.

Whip heavy cream with sugar and vanilla until soft peaks form. Spread or pipe over chilled pie. Dust with cocoa or top with chocolate shavings before serving.