1. Take a large bowl, and beat together heavy cream, sugar, and vanilla until stiff peaks form. Transfer half the whipping cream into another bowl; cover and refrigerate.
2. Now using rubber spatula, gently fold bananas into remaining whipped cream.
3. To prepare ice box cake, place a chocolate wafer in the center and place 6 more wafers in such a way that a circular shape would form. Then apply banana whipped cream over the wafers and then put another stack of 7 wafers in the same way but make sure that second layer cookies should overlap in between of the bottom layer cookies, then apply the banana cream over the wafers again and repeat the procedure until cookies finishes. Using 35 cookies you can make 5 stacks of 7 cookies.
4. Now over the last top layer of wafers, apply the plain whipped cream which you kept in fridge earlier and cover the entire stack properly. In the end sprinkle some grated chocolates on top and refrigerate till it sets completely. It would take at least 5 hrs. to get firm.