Place the Oreos in a large ziplock bag, seal, and crush with a rolling pin. Alternatively, cookies can be crushed in a food processor. Pour crushed cookies into a bowl, add the melted butter, and mix with a fork. Press crumbs into the bottom and up the sides of a 9-inch pie plate. Refrigerate while you make the filling.

In a large microwave-safe bowl, heat the milk chocolate in the microwave until smooth and melted. Add the cream cheese and hot chocolate mix. Beat with an electric beater until combined--mixture will look dry at this point. Add 1/2 cup of the marshmallow fluff, and continue to beat until smooth. Fold in the whipped topping.

Dollop tablespoons of half of the remaining marshmallow fluff evenly over the mixture. Gently and sparingly fold fluff into the filling (you still want streaks and globs of the fluff throughout), then immediately pour filling into the crust.

Drop more dollops of the remaining fluff evenly over the top, then swirl with a skewer or knife. Spoon whipped cream around the border, then sprinkle mini marshmallows and chocolate chips on top. Chill in the freezer for about 2 hours, or until set.

Pie is ready to eat straight from the freezer. For a softer consistency, allow the pie to sit out for about 15 minutes before serving.