16 ounces chocolate sandwich cookies such as Oreos (30-45 cookies), crushed
5 tablespoons unsalted butter, melted
flourless chocolate cake:
4 tablespoons (1/2 stick) unsalted butter
6 ounces dark chocolate (60 to 70 percent), chopped
2 tablespoons instant espresso powder
1/4 cup coffee, at room temperature
1/4 teaspoon salt
1 tablespoon pure vanilla extract
6 large eggs, separated, at room temperature
1 cup sugar
3/4 cup sugar
1/2 cup cocoa powder
1/4 cup cornstarch
1/4 teaspoon salt
4 large egg yolks
2 and 1/2 cups whole milk
3 tablespoons unsalted butter
2 teaspoons pure vanilla extract
3 ounces dark chocolate (60 to 70 percent), chopped
1 and 1/4 cups heavy cream
2 tablespoons granulated sugar
Make the cookie crust: Preheat oven to 300 degrees. Lightly spray a 9-inch springform pan with cooking spray. Line pan with parchment paper and lightly spray parchment and sides of pan. In a food processor, process cookies into very fine crumbs. Add melted butter and pulse until combined. Pour crumb mixture into prepared pan and press evenly with bottom of a measuring cup or glass, into bottom and up sides. Transfer to freezer for 10 minutes, then bake until dry to the touch, about 10 minutes. Transfer pan to a wire rack to cool.
Make the flourless cake: Increase oven temperature to 350 degrees. Place butter and chocolate in a heatproof bowl set over (but not touching) simmering water to melt; stir to combine. Remove from heat. In a small bowl, whisk together espresso powder, coffee, salt, and vanilla; set aside. In the bowl of an electric mixer fitted with the whisk attachment, beat egg yolks with 1/2 cup sugar until light and almost doubled in volume, about 5 minutes. Add melted chocolate mixture and beat until just combined. Scrape down sides and bottom of the bowl and mix on low speed for 5 seconds. Add coffee mixture and beat until just combined. Scrape down the sides and bottom of the bowl and mix on low for 5 seconds. Transfer to a mixing bowl. In the clean bowl of an electric mixer fitted with the whisk attachment, beat egg whites until foamy. Gradually increase speed to high and slowly add remaining 1/2 cup sugar, beating until soft peaks form. Transfer 1 cup egg white mixture to chocolate mixture and, using a rubber spatula, gently fold to combine. Add remaining egg whites and continue gently folding until they are almost completely combined; do not overmix. Pour into cooled cookie crust and bake for 38 to 42 minutes until cake is set but jiggles slightly. Transfer to a wire rack to cool completely. Cake will deflate in the center as it cools. Tightly wrap cooled cake with plastic wrap and refrigerate at least 3 hours and up to overnight.
Make the chocolate pudding: In a medium saucepan, whisk together sugar, cocoa powder, cornstarch, and salt. Add egg yolks and whisk until combined. The mixture will look like a thick paste. Slowly pour in milk, whisking constantly. Place saucepan over medium heat and bring mixture to a boil, whisking constantly to prevent it from burning on the bottom of the pan. Boil for 30 seconds and immediately transfer to a medium bowl. Add butter, vanilla, and chocolate; whisk until combined. Continue whisking until mixture is cooled slightly. Let stand at room temperature for 15 minutes. Press a piece of plastic wrap directly on the surface of pudding to prevent a skin from forming. Transfer to refrigerator until chilled, at least 3 hours and up to overnight.
Stir pudding to loosen and pour on top of cake. Using an offset spatula, spread pudding into an even layer. Transfer to refrigerator for 30 minutes.
Prepare whipped cream: In the chilled bowl of an electric mixer fitted with a chilled whisk attachment, beat cream until soft peaks form, about 2 minutes. Sprinkle sugar over cream and continue whisking until stiff peaks form. Spread whipped cream over pudding layer, working all the way out to the sides. Unmold cake and serve immediately.