For the Oreo Crust
25 Oreo cookies finely crushed
5 tbsp unsalted butter melted
For the Chocolate Mousse Filling
1 1/2 cups chopped semisweet chocolate 9 oz. (250g)
1 tsp vanilla extract
1 pinch of salt
3 cups heavy cream divided (720ml)
For the Decoration
2 tbsp sugar
3 Oreo cookies cut in half
1/3 cup chocolate shavings
Butter a 9-inch springform pan.
Combine finely crushed Oreo cookies and melted butter. Press into the bottom of the springform pan using the bottom of a flat measuring cup. Make sure it is compact. Chill for 30 minutes in the fridge.
Combine the chopped chocolate, vanilla extract, and the salt in a medium bowl.
In a small saucepan, bring 3/4 cup of the heavy cream to a bare simmer. Pour the cream over the chocolate, let sit for 1 minute, then whisk until smooth. Cover and chill in the fridge for about 20 minutes to cool.
Beat 1 1/2 cups heavy cream in a medium bowl with a hand mixer or stand mixer on medium-high speed to stiff peaks, about 2 minutes. Whisk the chocolate mixture to loosen it then fold it into the whipped cream with a silicone spatula until no streaks remain.
Scrape the chocolate mousse into the pan and gently spread it to the edges. Cover and refrigerate for at least 6 hours or overnight.
Just before serving, beat the remaining 3/4 cup of cream and 2 tbsp sugar with a hand mixer or stand mixer until the cream reaches stiff peaks. Pipe the borders of the cake using a large open star tip. Garnish with Oreo Cookie halves and chocolate shavings. This cake must stay refrigerated