Heat oven to 180°C. Grease bottom and side of springform pan, 22x7cm or 25x7cm, with shortening; lightly flour. Make cake mix as directed on box, using remaining cake mix, water, oil and eggs. Immediately pour into pan.
Bake 30 to 35 minutes or until toothpick inserted in center of cake comes out clean. Cool completely, about 1 hour.
Spread 340 grams fudge topping over cake; freeze about 1 hour or until topping is firm. In large bowl, mix ice cream and coarsely chopped candies; spread over cake. Freeze about 4 hours or until ice cream is firm.
In chilled medium bowl, beat whipping cream with electric mixer on high speed until stiff peaks form.
Remove side of pan; place cake on serving plate. Top with whipped cream. Melt fudge topping; drizzle over whipped cream. Garnish with additional candies.