What food to buy back from Hong Kong?

I'm curious, what are some of the must-buy food items to bring back from Hong Kong? Are there any local delicacies or snacks that are particularly popular and worth trying? Perhaps some unique flavors or ingredients that can't be easily found elsewhere? I'm interested in both sweet and savory options, and would love to hear your recommendations for the best places to purchase them. Additionally, are there any food items that are particularly good for gifting to friends and family who haven't had the chance to visit Hong Kong themselves?