Add the 24 OREO cookies to the bowl of a food processor. Process into fine crumbs. Then drizzle in the melted butter, and pulse until the crumbs combine with the butter. Press the crumb mixture into the bottom and sides of a deep-dish, 9-inch pie plate. Put it into the freezer while you prepare the filling.: The aroma of crushed OREO becomes intensely chocolatey, and when you drizzle in cooled melted butter the crumbs take on a glossy sheen that signals they are ready to be pressed. Press firmly into the base and up the sides so the crust holds together when sliced, feeling for an even thickness and checking the rim so it stands tall and uniform. A good press creates a compact, slightly springy surface. If the crust feels loose or falls apart when you lift it, you either need more butter or a firmer press. Freezing the shell for about 10 to 15 minutes firms it so the filling does not seep into the crumbs.
Add the heavy cream to a large bowl. Use an electric mixer to beat the cream to stiff peaks (1 or 2 minutes). Set the whipped cream aside.: Listen for the change in motor tone as the heavy whipping cream thickens, and watch for the glossy ropes forming on the beaters. Stiff peaks will hold a point without collapsing, and the whipped cream should feel light and cool against your skin if you dip a spoon. This airy texture is what keeps the filling from becoming dense. A common error is underbeating, which results in a loose filling, or overbeating, which makes the cream grainy and separated. If you overshoot, start again with a fresh batch of cream for stability.
In a separate bowl, use the electric mixer to combine the cream cheese, powdered sugar and vanilla until smooth and well-combined. Transfer the mixture to the bowl with the whipped cream, and use a rubber spatula to fold them together.: When you blend the room temperature cream cheese with powdered sugar and vanilla extract , you will notice the texture change from slightly tacky to velvety. Fold the whipped cream in gently to preserve air, turning the bowl with sweeping motions until the mixture looks uniform with no dark streaks. The filling should be buoyant and silky, not heavy or runny. Overmixing will deflate the whipped cream, so fold just until integrated. If small clumps of cold cream cheese remain, scrape the sides and beat them briefly before folding to avoid lumps in the final filling.
Add 9 OREO cookies to a zip baggie, and use a rolling pin or meat mallet to smash the cookies into small pieces. Stir the crushed cookies into the filling mixture. Scrape the filling into the frozen crust, and smooth the top. Refrigerate.: Smashing the additional OREO cookies by hand gives you imperfect chips that create delightful texture. As you stir them in, you'll see flecks of dark chocolate contrast with the pale filling, signaling the right ratio. Scrape the filling into the chilled crust and level it with a spatula so the surface is even and tidy. The filling should look plump and slightly glossy, and chilling helps set it firm enough to slice cleanly. If the filling seems too soft, refrigerate at least one hour; if it is too stiff because of cold ingredients, let it rest briefly at room temperature to ease spreading.
In a medium bowl, use an electric mixer to whip the heavy cream to stiff peaks. Add the whipped cream to a piping bag with a decorative tip, and pipe swirls along the edge of the pie (alternately, you can just spoon dollops of the whipped cream onto the pie). Place a whole OREO into each swirl of cream. Refrigerate until ready to serve.: Whipping the extra heavy whipping cream for topping should yield glossy, stable peaks that hold shape when piped. The sound will shift to a lighter, airy buzz and the cream will cling to the whisk. Pipe or dollop neat swirls around the rim, then gently nestle a whole OREO into each one for a classic look. The contrast of dark cookie and white cream is pleasing to the eye and palate. Chill the pie to let the garnish set; otherwise the cookies may soften when left out. A frequent mistake is piping straight from overwhipped cream, which can appear grainy and lose shine, so stop just shy of that stage.
