Excuse me, is three packs of five o'clock an authentic Cantonese dim sum?

Yes! "A cup of two pieces of morning tea, five points and three packs of snacks", Cantonese dim sum originated from morning tea, and the selected Cantonese dim sum is represented by "five points and three packs", three packs of barbecued pork, quicksand bag and fresh meat bag, and five points: shrimp dumplings, dried steamed dumplings, water chestnut cakes, glutinous rice chicken and steamed dumplings with corn and pork, all of which are classics.