Microwave hazelnut spread, uncovered, on HIGH for 25 seconds (be sure to completely remove foil wrap). Fold hazelnut spread and whipped topping together in a large bowl, leaving some chocolate streaks. Spoon mousse into a zip-top plastic freezer bag (do not seal). Snip 1 corner of bag to make a hole. Pipe mousse into parfait glasses. Serve with biscotti; or crush biscotti, and lightly sprinkle over each serving to provide the crunch.