Line a baking sheet with wax paper. Set aside. Place an assembled 8 or 9 inch springform pan in the freezer.
In a large saucepan over medium-low heat, add Nutella. Allow to melt somewhat, then add in cereal. Stir to coat. Dump onto prepared baking sheet, spreading out in an even, thin layer. Place in freezer and chill until hardened, about 30-45 minutes. Remove from freezer and break up into small clusters
While Nutella mixture hardens, place ice cream in fridge to soften (Depending on the brand you buy, it may soften more quickly. If the ice cream is softer straight from the freezer, leave less time for it to sit in the fridge) . When ready for assembly, scoop ice cream into a large bowl. Fold in cookie pieces. Remove springform pan from freezer. Working quickly, spread half of the ice cream mixture in an even layer in the pan. Top with half of Nutella rice krispies. Top that with remaining half of ice cream, again spreading evenly. Finish the cake by topping with the remaining rice krispies. Wrap in plastic wrap and return to freezer, allowing to chill until hardened, about 4-6 hours.
When ready to serve, release the springform pan. You may need to run a warm knife around the edges to be able to fully release the cake. Run a large knife under warm water, cut cake into slices, and serve immediately.