Blend cool whip and vanilla pudding mix using a mixer.Place in refrigerator for about 30 minutes.
Arrange 10 ice cream sandwiches in the shape you want your cake to be, on a dish or cookie sheet that is convenient for flipping the cake onto your serving dish when finished assembling.
Spread the first layer with cool whip mixture as if icing a cake.
Sprinkle this layer with Butterfinger crunch.
Place in freezer for 30 minutes.
Remove from freezer and add the remaining 10 ice cream sandwiches.
Cover this layer with cool whip mixture and sprinkle with Butterfinger crunch.
Place in freezer for 30 minutes.
Remove from freezer and flip onto serving platter with the last layer down.
Cover with remaining cool whip on sides and top.
Sprinkle top with Butterfinger crunch and drizzle with chocolate syrup.
Keep in freezer until ready to serve.
