Take for instance this Hong Kong street food staple, the eggette. It's really a lot like pancakes and waffles (except for the hint of coconut) but it looks a little more inviting because it looks different. And for HKD10, it's a cheap, healthy snack you can bring with you as you roam the shopping district that is Granville.
Two places I know for sure where you can find a stall is at Granville Road (at the corner of Shun Yee street). Another one is just past the camera shops along Cameron Road.