1. Prepare the Oreos:
* Separate the Oreos. Scrape the cream filling from about half of the cookies (12-15 cookies) and set the filling aside. You can add this filling to the cream cheese mixture later for extra Oreo flavor, or simply discard it if you prefer a less sweet mousse.
* Place all the Oreo cookie wafers (both the ones you scraped and the whole ones) into a food processor. Pulse until they are fine crumbs. If you don’t have a food processor, place them in a sturdy zip-top bag and crush them with a rolling pin or a heavy pan.
* For a crust (optional): If you want a crust layer, take about 1/2 to 3/4 cup of the Oreo crumbs and mix them with 4 tablespoons of melted unsalted butter. Press this mixture into the bottom of your serving glasses or a small trifle bowl. Chill while you prepare the mousse.
* Set aside about 1/4 cup of the remaining plain Oreo crumbs for garnish. The rest will go into the mousse.

2. Whip the Heavy Cream:
* Ensure your mixing bowl and whisk attachment (or hand mixer beaters) are clean and preferably chilled.
* Pour the 2 cups of cold heavy cream into the mixing bowl.
* Beat on medium-high speed until soft peaks form. Soft peaks are when the cream holds its shape somewhat but the peaks gently flop over when you lift the whisk.
* Gradually add 1/4 cup of the sifted powdered sugar while continuing to beat.
* Continue beating until stiff peaks form. Stiff peaks stand straight up when the whisk is lifted, or curl slightly at the tip, but hold their shape firmly. Be careful not to overbeat, or you’ll start making butter!
* Set the whipped cream aside in the refrigerator while you prepare the cream cheese base.

3. Prepare the Cream Cheese Base:
* In a separate large mixing bowl, place the 8 ounces of softened cream cheese.
* Add the remaining 1/4 cup of sifted powdered sugar and the 1 teaspoon of vanilla extract.
* If you saved the Oreo cream fillings, you can add them now.
* Beat with an electric mixer (you can use the same beaters, no need to wash if they just had cream on them) on medium speed until the mixture is completely smooth, creamy, and free of lumps. Scrape down the sides of the bowl as needed. This step is crucial for a non-lumpy mousse.

4. Combine and Fold:
* Gently fold about one-third of the whipped cream into the cream cheese mixture using a rubber spatula. This lightens the cream cheese base, making it easier to incorporate the rest of the whipped cream without deflating it. Use sweeping, circular motions, bringing the mixture from the bottom of the bowl up and over.
* Once partially combined, add the remaining whipped cream and continue to fold gently until just combined and no white streaks remain. It’s important to be gentle here to maintain the airiness from the whipped cream.
* Now, gently fold in the Oreo crumbs (reserving the portion for garnish). Fold until they are evenly distributed, but again, don’t overmix. A few streaks of cookie crumbs are perfectly fine.

5. Assemble and Chill:
* Spoon or pipe the Oreo mousse mixture into your prepared serving dishes (individual glasses, ramekins, a small trifle bowl, or the dish with the Oreo crust if you made one).
* If piping, you can use a piping bag with a large round or star tip for a neater presentation. If spooning, smooth the tops with the back of a spoon.
* Cover the dishes loosely with plastic wrap.
* Chill in the refrigerator for at least 4 hours, or preferably overnight. Chilling is essential for the mousse to set properly and for the flavors to meld. The longer it chills, the better the texture and taste.

6. Garnish and Serve:
* Just before serving, garnish your Oreo Mousse. Sprinkle with the reserved Oreo crumbs. You can also add a dollop of fresh whipped cream, a mini Oreo cookie on top, chocolate shavings, or a drizzle of chocolate sauce.
* Serve chilled and enjoy the delightful, creamy, Oreo-packed goodness!