line 8x4 inch loaf pan with foil. in large bowl, beat cream, sugar and vanilla with electric mixer on high speed until stiff peaks form.
spread 3/4 cup of the whipped cream evenly in bottom of pan. place 3 granola thins, chocolate side up, on top of cream. top with 3/4 cup whipped cream. sprinkle 1/2 cup of the cereal evenly on top. spread 3/4 cup of the whipped cream over cereal.
repeat layering with 3 granola thins and 3/4 cup whipped cream. top with remaining 1/2 cup cereal, 3/4 cup whipped cream and 3 granola thins. cover loosely with plastic wrap. freeze until firm, at least 4 hours or up to 2 days.
to serve, let cake stand at room temperature for 5 minutes. remove plastic wrap. place serving platter upside down over pan. turn platter and pan over.
remove pan and foil. break remaining granola thin into pieces, sprinkle over top. with sharp knife, cut crosswise into 1 inch thick slices.