Heat butter and oil in a large saucepan or deep frying pan over medium heat. Add onion. Cover. Cook, stirring occasionally, for 10 minutes or until starting to soften. Reduce heat to medium low. Cook, uncovered, stirring occasionally, for 20 minutes or until onion is very soft and starting to turn light golden.
Add sugar. Cook, stirring often, for 5 minutes or until sugar dissolves and coats onion well. Remove from heat. Cool. Transfer mixture to an airtight container. Refrigerate for up to 1 week.
Recipe courtesy of taste.com.au
Serving size 4