Blind Bake the Dough

Cup of Yum
1. Preheat oven to 375°F.
2. On a lightly floured surface, roll out the pie dough to about a 12-inch circle. Gently roll the dough around the rolling pin and carefully transfer it to a 9-inch pie dish. Gently press the dough into the dish and trim any excess from the edges. Fold over the top part of the dough (about a ½ inch). Use your fingers to crimp the dough, if desired (see video for reference).
3. Place the dish in the refrigerator for 1 hour, or in the freezer for 15 minutes. Preheat oven to 375°F.
4. Place parchment paper over the pie dough and fill it with pie weights, dried beans, or uncooked rice. Press into the bottom edges of the pie. Place in the oven for 25 minutes. Remove from the oven and carefully remove the weights and parchment paper. Bake for another 10 minutes, until lightly golden. Set aside while you make the rest of the pie.

Make the Meringue

1. In a large bowl, or in the bowl of your stand mixer, add the room-temperature egg whites and cream of tartar. Use a hand mixer (or your stand mixer) on medium to mix the whites with the cream of tartar until combined and frothy. Add the sugar and turn the speed up to HIGH. Continue mixing on HIGH until stiff peaks form, anywhere from 2 to 8 minutes (depending on the strength of your mixer). Set aside. Leave the oven on.

Prepare the Chocolate Filling

1. In a medium-sized saucepan, whisk together the sugar, cornstarch, and salt.
2. Whisk in the whole milk until fully incorporated and the dry ingredients have fully dissolved.
3. Over medium heat, bring the mixture to a simmer, about 4 to 5 minutes. The mixture will thicken.
4. Turn off the heat and stir in the chocolate and continue stirring until fully melted. Stir in the egg yolks and continue stirring until all yolk streaks are gone and the mixture is smooth.
5. Turn the heat back on to medium and bring to a puttering simmer. Turn off the heat and use your spatula to scrape down any of the chocolate on the side of the pan. Turn the heat back on and simmer for another 2 minutes. Turn off the heat and stir in the butter and vanilla. Stir until butter has melted and is incorporated.

Finish the Pie

1. Pour the hot chocolate filling into the prepared pie crust.
2. Immediately spoon the meringue onto the hot filling. Spread the meringue to the edges of the crust, using your spatula to help anchor it to the sides.
3. Place the pie in the 375°F oven for about 10 to 15 minutes, until the tips of the meringue are browned. Remove the pie and place it on a baking rack on the counter for 1 hour. Chill the pie for 2 to 3 hours.
4. To slice the chilled pie, place a sharp knife in a tall glass of hot tap water. Slice and serve.