Mix flour, butter and pecans until finely crumbled and pat into 9x11-inch pan. Bake at 350°F for 15-20 minutes.
Layer bananas on top of slightly cooled crust.
Beat sugar and cream cheese until smooth. Fold in 4 oz. Cool Whip and spread over bananas.
Mix dry puddings together and beat with milk until thick. Spread on top of middle layer. Spread remaining Cool Whip on top. Garnish with grated chocolate bar. Refrigerate for several hours before serving.