1. Make the Crust

1. Crush the Oreos into fine crumbs using a food processor.
2. Mix with melted butter until evenly moistened.
3. Press the mixture firmly into the bottom and sides of a 9-inch pie dish.
4. Refrigerate while preparing the mousse.

2. Prepare the Chocolate Mousse

1. Melt the chopped chocolate and butter in a heatproof bowl set over simmering water. Let cool.
2. In a second heatproof bowl, whisk egg whites, sugar, and cream of tartar.
3. Place the bowl over simmering water and whisk until sugar dissolves and mixture reaches 160°F.
4. Remove from heat and beat until glossy stiff peaks form.
5. In another bowl, whip the cold heavy cream to soft peaks.
6. Fold the cooled chocolate into the egg whites, then gently fold in the whipped cream.
7. Stir in the crushed Oreos.
8. Spoon mousse into the chilled crust and smooth the top. Refrigerate 6 hours or overnight.

3. Make the Whipped Cream

1. Beat heavy cream, sugar, and vanilla until stiff peaks form.
2. Spread or pipe on top of the chilled pie.
3. Garnish with chocolate curls.