In a food processor, add the Oreos and pulse until they become fine crumbs. Add the melted butter and mix until combined.

Press the Oreo mixture into the bottom and sides of a 9” pie dish, packing it in with the back of a spoon or a small cup. Place in the freezer while you make the chocolate mousse filling.

In a medium bowl, whisk together the egg yolks and 66g (⅓ cup) sugar until it's pale in color and flows off of the whisk. Then, place over a small pot of simmering water, whisking frequently until it reaches 160 F.

Turn the heat down to low and mix in the chocolate and vanilla until fully melted. It will turn into a thick, fudge-like consistency. Set aside to cool for a few minutes.

In the bowl of a stand mixer fitted with the paddle attachment, cream the butter on medium speed for 2-3 minutes until light and fluffy.

Add in the egg yolk, chocolate mixture, then turn the mixer up to high speed for about 3 minutes until fluffy. Don’t worry if it starts to split, it will all come together once the meringue is added!

In a separate medium bowl, whisk together the egg whites and remaining sugar. Place over a small pot of simmering water, whisking frequently until it reaches 160 F. Remove the bowl from heat and use an electric hand mixer to beat until stiff peaks form.

Gently fold the meringue into the into the chocolate mixture until no white streaks are left.

Pour the chocolate mousse filling into the Oreo crust and smooth out the top with an offset spatula. Place in the fridge to chill for at least 3 hours or overnight.

Just before serving the pie, make the whipped cream.

In a large measuring cup or bowl, add the cold heavy cream and sugar. Use an electric mixer to whip the cream until stiff peaks form. Careful not to over-whip the cream, as it can quickly split and become grainy!

Top the pie with the whipped cream, and add chocolate shavings, if desired. Enjoy!