Prepare the crust by combining chocolate cookie crumbs, melted butter, and sugar in a bowl until evenly moistened. Press firmly into the bottom and slightly up the sides of a 9-inch springform pan. Refrigerate for at least 30 minutes to set.
Make the caramel sauce by combining sugar and water in a medium saucepan over medium heat. Do not stir after this point! Swirl the pan occasionally until the mixture turns a deep amber color (about 8-10 minutes). Carefully add the heavy cream (it will bubble vigorously), then whisk in butter and salt until smooth. Set aside 2 tablespoons for garnish and allow the rest to cool completely.
Create the peanut butter layer by beating cream cheese and peanut butter with an electric mixer until smooth. Add powdered sugar and vanilla, mixing until fully incorporated. Gently fold in the whipped cream until no streaks remain, being careful not to deflate the mixture.
Pour cooled caramel sauce over the chilled crust, creating an even layer. Refrigerate for 15 minutes to set slightly before proceeding to the next step.
Spread the peanut butter layer carefully over the caramel layer, smoothing the top with a spatula. Return to the refrigerator while preparing the chocolate mousse.
Prepare the chocolate mousse by melting chocolate and butter together in a heatproof bowl set over simmering water (or microwave in 30-second intervals, stirring between each). Allow to cool slightly but remain fluid.
Beat egg yolks and sugar in a separate bowl until pale and thick (about 3 minutes). Gradually whisk in the melted chocolate mixture until fully incorporated.
Whip egg whites in a clean bowl until stiff peaks form. In another bowl, whip the heavy cream with vanilla until soft peaks form.
Fold whipped egg whites into the chocolate mixture first, then gently fold in the whipped cream until just combined, maintaining as much air as possible in the mixture.
Carefully spread the chocolate mousse over the peanut butter layer, creating a smooth, even top. Refrigerate the entire pie for at least 4 hours or preferably overnight.
Before serving, garnish the pie with chopped peanuts, chocolate shavings, and a drizzle of the reserved caramel sauce. Carefully remove the springform ring before slicing.