Pineapple is a symbol of prosperity for the Chinese, and originally these cakes, much bigger and rounder when first created, were only sold for the mid-Autumn festival and for engagements in Taiwan (very similar to mooncakes in mainland China). Nowadays, they have transformed to the traditional square, and can be given as gifts year-round. Inside the shortbread pastry, made with flour, milk powder, butter (originally lard), egg, sugar and shortening (from palm and/or soybean oil), is a pineapple jam, made, as I read, paired with white gourds, which gives it a better texture and flavour.
These are quite tasty, and I can see why they are much beloved. They are definitely sweeter than the Singaporean version, though no less good. I found this particular brand in almost any Chinese supermarket in Mississauga.