Gather all ingredients.

Line a 9-inch springform pan with 2 layers of plastic wrap, leaving a 2-inch overhang around edges.

Process cookies in a food processor until crushed into very fine crumbs, about 45 seconds. With food processor running, add melted butter and salt; process until well combined, about 10 seconds. Transfer mixture to prepared cake pan; press crumbs evenly into bottom of pan. Transfer, uncovered, to freezer; freeze until hardened, about 15 minutes.

Meanwhile, remove ice cream from freezer, and let stand at room temperature until slightly softened, about 15 minutes. Transfer ice cream to a large bowl, and fold in Butterfinger pieces. Remove pan from freezer, and pour ice cream mixture evenly over crust in pan, and smooth with an offset spatula. Gently tap pan on counter to release any air bubbles. Cover and freeze for at least 4 hours.

Beat heavy cream and peanut butter with an electric mixer on medium speed until slightly thickened, about 1 minute. With mixer running on medium, gradually add powdered sugar. Increase speed to medium-high, and beat until medium peaks form, about 1 minute.

Remove ice cream cake from freezer, and carefully remove springform pan and plastic wrap. Gently slide ice cream cake onto a cake stand or serving platter. Quickly but gently spread whipped topping over top and sides of cake. Drizzle with warm fudge topping; sprinkle top with additional Butterfinger pieces. Freeze at least 1 hour or up to 2 days before serving.