|Preparation Time||10 minutes|
|Cooking Time||40 minutes|
|Serves||2 x 500ml jars|
|40ml butter||150ml red wine vinegar|
|750g onion, thinly sliced||15ml black mustard seed|
|200g soft brown sugar|
- Heat the butter in a large, heavy-based pan and cook the onions for about 10 minutes, until softened and slightly brown.
- Stir in the remaining ingredients and cook, uncovered, for a further 25-30 minutes, stirring occasionally. The onions should turn soft, light brown and caramelize slightly.
- Ladle into hot sterilised jars and seal immediately.
- Once cooled, refrigerate for up to 1 week.