Line the bottom of a 9-inch springform pan with a round of parchment paper. 2. In a medium bowl, combine chocolate wafer crumbs, melted butter, and sugar. Press firmly into the bottom of the pan. Freeze for 15 minutes. 3. Spread softened vanilla ice cream evenly over the crust. Smooth the top with an offset spatula. Freeze for 1 hour until firm. 4. Spread softened chocolate ice cream over the vanilla layer. Smooth and freeze for at least 4 hours, or overnight. 5. Make the frosting: In a large chilled bowl, combine heavy cream, powdered sugar, vanilla, salt, and pudding mix if using. Beat on medium-high speed until stiff peaks form—when you lift the beaters, the cream stands straight up. Do not overbeat, or it will turn buttery. 6. Remove the cake from the springform pan. Place on a serving plate. 7. Frost the top and sides with the whipped cream, working quickly. Use the offset spatula for smooth swirls. 8. Press mini chocolate chips onto the sides if desired. Freeze for at least 2 hours before serving. 9. To serve, let the cake sit at room temperature for 5-10 minutes for easier slicing. Use a sharp knife dipped in hot water and wiped dry between cuts.