Place Oreos in your food processor and pulse about 20 times, until they become fine crumbs. If you do not have a food processor, place them in a zip-top bag. Press the air out, and then smash them with a rubber mallet or crush with a rolling pin.Pour in melted butter and mix well.
Pour into a pie plate or springform pan and press firmly into the bottom and sides of the pan.Place in the refrigerator while preparing the batter.
Fudgy Chocolate Cake Layer
Preheat oven to 350 degrees.
Do not prepare the brownies according to package directions. Instead, mix together the dry brownie mix, melted butter, espresso powder, and eggs.
Pour over the Oreo crust and bake for 30 minutes, until edges are set and cracks have started to form on the top.
Cool completely, at least 90 minutes. May be made a day ahead.
Stabilized Whipped Cream
In a large mixing bowl, beat the heavy cream with a whisk attachment on medium-high speed until it begins to thicken.Add in the sugar, vanilla extract, and cream of tartar. Turn mixer onto high speed and continue to beat until soft peaks form. Remove 2 cups to fold into the pudding, and refrigerate the remaining whipped cream until ready to layer on the pie.
Chocolate Pudding Layer
In a large bowl, whisk together the pudding mix and cocoa, ensuring there are no large cocoa clumps. Add in milk and vanilla, and whisk for 2 minutes. Let stand for an additional 5 minutes to thicken.Gently fold in 2 cups of prepared stabalized whipped cream.Refrigerate until ready to use. Once the fudge cake layer has cooled for at least 90 minutes, spread the pudding layer over the top and refrigerate for at leaset 2 hours.
Topping the Pie
When ready to serve, spread the remaining whipped cream over the pudding.