Prepare pie crust by lining a 9″ pie plate, and baking at 350º until just beginning to brown
Meanwhile, combine milk, sugar, cornstarch, and cocoa powder
Heat over medium heat, stirring frequently. Your cocoa powder won’t want to dissolve until the milk gets warm, so don’t worry too much if your chocolate milk looks lumpy at first, but do make sure the cornstarch is mixed in before it gets hot
Continue cooking until milk is bubbly and thick
Remove from heat and stir in chocolate chips until melted and fully incorporated
Pour into baked pie shell, and let cool until no longer hot
Cover with plastic wrap, and refrigerate overnight
Before serving, Beat heavy whipping cream, powdered sugar, and vanilla together until stiff peaks form