Rogan josh curry sauce (although most other curry sauces are also good). Chips and curry sauce is a really popular fast food in the UK, but the curry sauce in question is much closer to a brown sauce than it is to anything that's usually associated with the word "curry". So I make my own curry sauce and put it on instead. This does, of course, completely ruin the "fast" part of "fast food", but it is very tasty