But because onions have a high sugar content, and sugar easily burns, both of these cooking methods risk burnt onions. In other words, onions are easy to burn. And once a small sliver of onion ...

Low and slow or fast and furious? How you cook your onions can transform a simple hot dog from humdrum to gastronomic delight, here's how to get it right.

For the burnt-onion ketchup, heat a tablespoon of the oil in a large non-stick frying pan over a high heat. Add a small handful of the sliced onions and fry until dark golden-brown and almost charred.