Caramelised Onion Grilled Cheese

Method

1. Add 1 tablespoon of butter to a stainless steel or cast iron pan on a low-medium heat. As soon as it has melted, add the onion and a pinch of salt, then cook for 50-60 minutes, stirring frequently until the onion is a dark golden brown. If necessary, add splashes of water to prevent the onion burning and use the water to deglaze the pan.
2. When the onion looks ready, stir in the sugar and vinegar, then continue cooking for 5 minutes.
3. Spread the mayonnaise over one side of each slice of bread. Then add the bread slices, mayonnaise side down, to a pan on a medium heat.
4. Spread the mustard over one slice of bread, then cover both slices evenly with cheese. Next add the caramelised onion over one of the slices, then flip the other slice of bread on top so the onion is sandwiched in the middle.
5. Cook for 3-5 minutes on each side or until the bread is golden brown and the cheese is melted, pressing down occasionally with a spatula to compress the sandwich. Remove the sandwich from the pan and slice to serve.