How to Make It
Preheat oven to 350°F. Cut a 9-inch round piece of parchment paper, and line bottom of a 9-inch springform pan. Coat parchment-lined pan with baking spray; set aside.
Beat together cake mix, water, oil, and eggs in the bowl of a stand mixer fitted with a paddle attachment on low speed for 10 seconds. Increase speed to medium, and beat 2 minutes. Pour 2 cups of the batter into prepared pan. Bake in preheated oven until set, about 20 minutes. (Reserve and bake remaining batter for a few cupcakes, if desired.)
Allow cake to cool completely at room temperature, about 30 minutes. Freeze 15 minutes. While cake freezes, remove ice cream from freezer, and allow to soften slightly at room temperature.
Spread softened ice cream evenly over cake layer; freeze 30 minutes.
Spread whipped topping evenly over ice cream layer, and place candies around top of cake. Freeze at least 1 hour or until ready to serve. Slice and serve immediately.