8ounceschocolate wafer cookies (such as Nabisco Famous Wafers)
8ouncesbittersweet chocolatefinely chopped plus more for garnish
2quarts (4 pints)Ice cream(use peanut butter, chocolate, vanilla, coffee, or a combination of them)
2cupschilled heavy creamdivided
Unsweetened cocoa powderfor garnish
Roasted salted peanutsfor garnish
For the crust: Using a pastry brush, coat the inside of a 9-inch springform pan with 1 tablespoon of the melted butter. Cut parchment or waxed paper into a circle the same size as the base of the pan and place it in the base.
Place cookies in the bowl of a food processor and pulse until ground; add remaining 6 tablespoons melted butter and pulse until mixture is moistened. Press mixture evenly and firmly into the bottom of the prepared pan and freeze until it’s good and set, about 30 minutes. Meanwhile, take the ice cream out of the freezer to soften and make the ganache.
For the ganache: Place chocolate in a medium heatproof bowl; set aside. Place 1 cup of the cream in a small saucepan over medium heat and bring to a simmer. Pour cream over chocolate and let stand until chocolate has melted, about 5 minutes.
Stir gently until smooth then stir in remaining butter, one piece at a time, until completely incorporated; let cool slightly before using. Meanwhile, let the ice cream soften, for another about 15 minutes, or until soft enough to spread like room temperature butter but not melted.
For the assembly: When ice cream is softened, transfer to a mixing bowl. Using a rubber spatula mix until spreadable. Spread half of the ice cream over the cookie crust and smooth the top. Pour half of the ganache over the top and smooth and place in the freezer until firm, at least 30 minutes. Place the remaining ice cream back in the freezer as well.
Remove peanut butter ice cream from the freezer and let soften about 15 minutes. Mix again until spreadable. Spread peanut butter ice cream over the fudge, level the top of the cake, add remaining ganache (you may want to reheat this slightly until it’s just pourable), smooth it, and freeze until the whole cake is very firm, at least 3 hours and up to 1 day.
To serve: Remove cake from the freezer and let sit at a few minutes at room temperature before cutting. Meanwhile, place remaining 1 cup of whipped cream in a clean, large bowl and whip with a whisk until soft peaks form. Top cake with whipped cream, cocoa, peanuts, chocolate shavings, and serve.