Since the early 20th century, much of Japanese cuisine has taken inspiration from Western cuisine. It's a genre the Japanese call yoshoku ("Western food"). That fascination can lead to the obsessive replication of classic dishes, which is why you're just as likely to find excellent pizza in Kyoto as you are in Naples. But it can also lead to the reinterpration of Western staples into something uniquely Japanese.
The katsu sando is a great example of yoshoku. A katsu (a shortening of the Japanese word for cutlet, katsuretsu) is breaded and fried, and sandwiched between two slices of shokupan, fluffy white Japanese milk bread. Sando is the Japanese abbreviation of sandoitchi, which means sandwich. It's a triple-threat of a blockbuster snack: photogenic, texturally interesting and deliciously moreish.
Katsu sandos are everywhere in Sydney right now, and only getting more popular. Here are the best places in town to get your hands on one.