Preheat oven to 375 degrees. Place the Oreo cookies and butter in the food processor and pulse until you have fine crumbs. Press into a springform pan or 9-inch deep pie pan. If you use a classic 9-inch pie pan, you will have a lot of extra Oreo crust. I prefer to use a springform pan. Bake for 8 minutes. Let cool. If you want to make this no-bake, place the oreo crust in the freezer for 15 minutes.
Make the filling by creaming together with a mixer or in a food processor, the Nutella, cream cheese, and powdered sugar until smooth and creamy.
In another bowl, beat the whipped cream until soft peaks form. Carefully fold into the chocolate Nutella cream mixture, until no white streaks remain.
Spread evenly onto the cooled crust, cover, and place in the refrigerator while you make the chocolate ganache.
To make the chocolate ganache, place the chocolate and heavy cream in a microwave-safe bowl. Heat at half power in 30-second increments, stirring after each time until the chocolate is melted and creamy.
Remove the pie from the refrigerator, and pour chocolate ganache over the pie, and spread with a spatula. Let chill for 3-4 hours.
When ready to serve, make homemade whipped cream and pipe onto the pie. If you desire, place ferrero rocher chocolates around the pie and sprinkle with hazelnuts.
Notes
Chocolate Ganache -- use your favorite type of chocolate depending on if you want it to be a dark chocolate ganache or a milk chocolate ganache or a mixture of both. I like to do half milk and chocolate and half semi-sweet chocolate.