Preparation Steps

• Preheat your oven to 350°F and line a baking sheet with parchment paper. Chop the Oreo cookies into chickpea-sized pieces, toss them with melted butter, then spread them onto the prepared sheet. Bake until fragrant and crisp, about 5 to 8 minutes.
• Melt chocolate chips in a medium heatproof bowl using a microwave. Heat them in 30-second increments, stirring in between, until fully melted and smooth—this should take around 60 to 90 seconds total. Stir in the coconut oil or vegetable shortening.
• Combine the cookie crumbs with the melted chocolate mixture, tossing well to coat. Spread this mixture onto another parchment-lined sheet and refrigerate until hardened, which should be around 30 minutes. After that, chop it into small pieces for added crunch.
• Prepare a 9" springform pan by lining it with plastic wrap. In a large bowl, stir the vanilla ice cream until it's smooth and spreadable. Spoon it into the bottom of the prepared pan and place it in the freezer for about 30 minutes to harden slightly.
• Warm the fudge topping by microwaving it in 15-second increments, stirring in between each time, until it's slightly warmed and spreadable. This should take about 30 to 45 seconds total.
• Layer the chocolate crunchies on top of the frozen vanilla ice cream. Dollop the warm fudge across the crunchies and use an offset spatula to carefully spread it. Freeze the cake until slightly firm, approximately 15 to 30 minutes.
• Stir the chocolate ice cream until it’s smooth and spreadable. Spoon it over the fudge layer and gently spread it until it's smooth. Freeze until firm, which may take at least 4 hours or even a week if you’re prepping ahead.
• Invert the frozen cake onto a platter about 2 hours before serving. Peel off the top plastic wrap layer, making sure the chocolate layer is now at the bottom. Remove the sides of the springform pan and peel off the remaining plastic wrap. Return it to the freezer while you whip the cream.
• Beat the heavy whipping cream, confectioners' sugar, and vanilla extract in a large bowl until stiff peaks form. Transfer about one-third of the whipped cream into a piping bag fitted with a star tip for decoration.
• Spread the remaining whipped cream generously over the top and sides of the cake. Pipe a decorative shell border around the top edge and base, if desired. Freeze the decorated cake uncovered for 1 to 2 hours before serving.
• Decorate the edges and base of the cake with sprinkles just before serving. Allow it to sit at room temperature for about 5 minutes, then cut into slices using a sharp knife.