Start by mixing the all-purpose flour and salt in a large mixing bowl. Cut in the shortening until the mixture resembles coarse crumbs. Gradually add ice water, mixing until the dough comes together. Shape into a ball, wrap in plastic wrap, and refrigerate for at least 30 minutes.
Once the dough has chilled, roll it out on a floured surface to about 1/8-inch thick. Transfer it to your pie pan, press it into the edges, trim excess dough, and crimp the edges. Poke a few holes in the bottom with a fork.
Preheat your oven to 350°F (175°C). Place parchment paper over the crust, fill with pie weights or dried beans, and bake for about 15 minutes. Remove weights and parchment, bake for an additional 10 minutes until lightly golden. Allow to cool completely.
In a medium saucepan, whisk together the sugar, cornstarch, cocoa, and salt. Gradually stir in the whole milk and evaporated milk. Cook over medium heat, stirring constantly, until thickened. Remove from heat.
In a separate bowl, beat the egg yolks. Gradually whisk in about 1 cup of the hot chocolate mixture to temper them, then pour back into the saucepan and cook for an additional minute. Remove from heat and stir in the butter and vanilla extract.
Pour the chocolate filling into the pre-baked pie crust, smoothing the top with a spatula. Allow to cool slightly while preparing the meringue.
In a clean mixing bowl, beat the egg whites with cream of tartar until soft peaks form. Gradually add sugar, continuing to beat until stiff peaks form and meringue is glossy.
Spread the meringue over the chocolate filling, sealing the edges to prevent shrinkage. Create peaks for a decorative finish.
Bake the pie at 350°F (175°C) for about 10-12 minutes, until the meringue is golden brown. Watch closely to avoid burning.
Allow the pie to cool at room temperature for at least 2 hours before slicing. Serve chilled or at room temperature and enjoy!
