Add your 4 egg yolks to a small bowl and beat well with a fork. Set aside.

 

In a medium saucepan, add sugar, flour, and cocoa and whisk to combine. Add your milk and whisk well to incorporate and dissolve the dry ingredients. 

 

Cook over medium heat, stirring constantly, until the mixture is warm, but not boiling. Dip out about 1/2 cup and add to your egg yolks. Mix until smooth and then slowly add them to the saucepan. Continue cooking, stirring constantly, until the pudding comes to a full, slow boil and gets thick. 

 

Remove from the heat and add in the vanilla, stirring to incorporate. 

 

Allow to cool slightly, stirring occasionally, and then pour into your prepared crust. 

 

Place a piece of plastic wrap directly over the pudding, lightly patting it onto the surface to create a fake "skin". Place in the refrigerator for 1-3 hours or overnight. 

 

Remove the plastic wrap before serving and add cool whip or fresh whipped cream to the top for garnish. Enjoy!