In a large mixing bowl whip the cream for 3-4 minutes with the mixer on high speed. Add powdered sugar and beat for another 1-2 minutes until the cream becomes very thick.
In a medium rectangular or round pan arrange 1 layer of broken cookies/ crackers so that they cover well the bottom of the pan. Spread on top half of the dulce de leche (mix it well first so that its consistency becomes runnier). Cover with a layer of banana slices. Sprinkle⅓ of the ground hazelnuts on top of the bananas. Cover with half of the whipped cream.
Repeat the process one more time, finishing all the prepared ingredients. On top of the second layer of whipped cream sprinkle ground hazelnuts and chocolate sprinkles (if using).
Let the cake stay 4 to 6 hours in the fridge before serving.
Notes
Store the cake for 2-3 days in the fridge, covered.