Prep: 30 minutes
Total: 5 hours
2 1/2 cups heavy cream
1/4 cup confectioners' sugar
4 teaspoon vanilla extract
1 cup whole milk
1/2 cup light brown sugar
2 tablespoons cornstarch
2 egg yolks
6 tablespoons unsalted butter
pinch of kosher salt
3/4 cup smooth peanut butter
3 (10 ounce) packages of Oreo Thins
1/2 cup cocoa powder
1/2 cup granulated sugar
1. In a large bowl, whip 2 cups|500 ml of the cream, confectioners' sugar, and 1 teaspoon|4 grams of the vanilla until stiff peaks form.
2. Place the peanut butter in a medium bowl. In a small saucepan, combine the milk, brown sugar, cornstarch, and egg yolks over medium heat. Cook, stirring constantly, until thick, about 5 minutes. Remove from the heat and stir in 1 teaspoon|4 grams vanilla, 2 tablespoons|30 grams of the butter, and the salt and pour over the peanut butter, whisking, until slightly smooth. Cool slightly, then beat in half of the whipped cream until smooth.
3. Line an 8-inch-by-8-inch square baking dish with cling film with about 2-inches hanging over the sides.
4. Lay 16 Oreo cookies in the bottom of the baking dish in an even layer. Top with 1/3 of the whipped cream and spread it out into an even layer.
5. Top the whipped cream layer with 16 more Oreo cookies, then top with 1/3 of the peanut butter mousse.
6. Repeat twice more with both the whipped cream and peanut butter mousse, alternating layers and finishing with the peanut butter mousse. Cover with cling film and refrigerate or freeze for at least 4 hours.
7. Meanwhile, in a small saucepan, whisk the remaining cream with the cocoa powder and the granulated sugar over medium heat. Cook, stirring, until the sugar has dissolved, about 5 minutes. Stir in the remaining vanilla and butter and whisk until smooth. Fudge sauce will keep, refrigerated, for 2 weeks. When you're ready to use it, simply microwave it for 30 seconds at a time, stirring after each time, until soft. Makes about 1 cup.
8. To serve, using the sides of the cling film, lift the icebox cake out of the baking dish and transport it to a serving dish. Slice it and serve it with chocolate sauce.