• Heat the oven to 350º. Unwind Oreos, scrape off cream and then add chocolate cookies and salt to the bowl of a food processor or blender. Pulse or whir until finely ground. Add the butter and pulse just until crumbs stay together. Press cookie mixture into a 9-inch pie dish, evenly. Bake about 15 minutes. Let cool.

For the Filling

• Add 3/4 cup heavy cream and espresso powder to a saucepan over medium heat. Whisk until espresso has dissolved and heat until hot, but don't simmer. About 1 minute.
• In a bowl, add the egg yolks, sugar, and salt and whisk to combine. Slowly pour in the hot cream and whisk. Transfer the mixture back to the sauce and continue to cook over low heat. Stir constantly, until the liquid coats the back of a spoon, about 3-4 minutes.
• Remove pan from heat. Add the chopped chocolate and vanilla and whisk till smooth. Let cool to room temp, stirring occasionally, about 40 minutes.
• In a medium bowl, add 1 1/4 cups heavy cream and beat with a hand mixer on medium speed until stiff peaks form, about 4 minutes. Pour chocolate mixture over the whipped cream and fold, using a spatuls, until just combined. Carefully pour the chocolate mousse into the pie crust and transfer to the refrigerator to chill for six hours or overnight.

For the Topping

• Add 1 cup heavy cream to a medium bowl and beat with a hand mixer on medium speed until soft peaks form, about 3 minutes. Add the powdered sugar and continue to beat until stiff peaks form, 1 more minute.
• Take pie from the refrigerator. Dump the whipped cream into the middle of the pie and using a spatula, spread to the edges, leaving about an inch of space between the crust and whipped cream so you can still see the chocolate. Decorate with your favorite fancies. Or not.