Step 1

Heat a large heavy-based saucepan over high heat. Melt butter and oil, and cook until butter is foamy. Add onion, garlic and thyme. Increase heat to medium and cook, stirring frequently, for 40 minutes or until slightly golden and catching on the base.

Step 2

Add Vegemite and quince paste, and cook for a further 5 minutes or until melted, then stir in cornflour. Increase heat to high, add vinegar and verjuice, and cook, scraping the bottom of the pan with a spoon, for 2-3 minutes until syrupy.

Step 3

Add 1L (4 cups) water and bring to the boil. Reduce heat to low and cook for 15-20 minutes until reduced and thickened.