Step 1: Make the Crust

1. In a medium bowl, mix the crushed Oreos and melted butter until well combined.
2. Press the mixture firmly into the bottom and up the sides of a 9-inch pie dish.
3. Place in the refrigerator to chill while you prepare the filling.

Step 2: Make the Chocolate Filling

1. In a large saucepan over medium heat, whisk together the whole milk, sweetened condensed milk, and cocoa powder until smooth.
2. Cook, stirring constantly, until the mixture thickens slightly (about 5-7 minutes).
3. Remove from heat and stir in vanilla extract.
4. Let the mixture cool to room temperature.
5. Once cooled, fold in the thawed whipped topping until fully incorporated and the filling is light and fluffy.

Step 3: Assemble the Pie

1. Pour the chocolate filling into the prepared Oreo crust.
2. Smooth the top with a spatula.
3. Cover and refrigerate for at least 4 hours, or until fully set.

Step 4: Add Toppings and Serve

1. Just before serving, top the pie with extra whipped cream, crushed Oreos, chocolate shavings, and cherries if desired.
2. Slice and serve chilled for the best texture and flavor.