1-First, combine 1 cup sugar, 4 heaping tablespoons cocoa powder, 3 tablespoons cornstarch, and a pinch of salt in a pan. Stir in 2 cups whole milk and bring the mixture to a boil for 1 minute.

2-Beat 4 egg yolks separately, then gradually add a small amount of the hot milk mixture while stirring to temper the eggs.

3-Return the egg and milk mixture to the pan and stir constantly over medium heat for about 3 minutes until it thickens. Remove from heat and mix in 1 teaspoon vanilla extract, 2 tablespoons butter, and 1/4 cup semi-sweet chocolate chips until everything melts smoothly.

4-Pour the hot filling into the 9-inch pre-baked pie crust and set it aside.

5-For the meringue, beat 4 egg whites with a pinch of salt and 1/4 teaspoon cream of tartar until stiff peaks form. Gradually add 1/4 cup sugar and a few drops of vanilla extract, beating until glossy.

6-Spread the meringue evenly over the hot filling, sealing it completely to the edges of the crust. This step helps prevent weeping and keeps everything together.

7-Bake at 325°F (163°C) for about 20 minutes or until the meringue turns golden brown. Let the pie cool before serving to set the flavors.