Add oreos to a food processor. Pulse until the oreos are broken down into crumbs. Transfer to a medium bowl with 4 tablespoons melted butter.
Stir together butter and oreos with a fork until mostly combined. Transfer to a 9" pie plate and pat into an even layer on the bottom and up the sides of the dish to form a crust. Refrigerate for at least 15 minutes before using to allow the oreos and butter to firm up.
In a stand mixer with the whisk attachment, add 1 cup of heavy whipping cream. Whip on medium-high speed until you reach soft peaks, about 1.5 to 2 minutes. (Soft peaks: the cream can mostly stand up on its own but falls over at the top).
Stop the mixer and sift in the 2 tablespoons powdered sugar and cocoa powder. Continue whisking on medium-high speed until you reach stiff peaks. The whipped cream will hold its shape when lifted up but still be light and fluffy. Gently transfer whipped cream to a bowl and place in the fridge until ready to use.
To the same bowl you used to make the whipped cream, add the cream cheese and peanut butter. You don't need to clean out the bowl between steps. Cream together on medium speed until smooth and fluffy, scraping down the sides as needed.
Add the remaining ¾ cup powdered sugar and mix until well combined.
Once combined, use a spatula to fold in the chocolate whipped cream. Remove the chilled pie crust from the fridge. Add the filling to the center of the pie, spreading outward to the edges with a spatula until smooth.
Optional: To melt the chocolate, add one inch of water to a small to medium sauce pot over medium heat. Once simmering, place a heat safe bowl on top to make a hot water bath. Add the chocolate to the glass bowl. Stir until melted.
Use a spatula to drizzle chocolate across the top of the pie (optional). Cover and let chill in the fridge for at least 4 hours or freeze for 1 hour before serving.
Heavy whipping cream works better for whipped cream than heavy cream because it's higher in fat.
Peanut butter: Choose a traditional peanut butter (one that doesn't have oil separation). The oil separation in natural peanut butter can affect the texture of the pie.
Storage: For best quality serve within 1-2 days. Keeps for up to 3-4 days.
Freezing instructions: This pie freezes well for up to 3 months. Cover tightly with a lid or foil before freezing. When ready to eat it will thaw quickly at room temp but is delicious eaten frozen.
Check out my YouTube video above where I share step by step instructions on how to make chocolate peanut butter pie.