Step 1

Toast mustard seeds in a saucepan over medium heat for 1 minute or until fragrant and starting to pop. Add the oil and onion, then cook, stirring, for 1-2 minutes until onion is softened but not coloured.

Step 2

Add the remaining ingredients and 2 tsp salt, and stir to combine. Bring to a simmer, reduce heat to low and cook, stirring occasionally, for 30-40 minutes until reduced and thickened. Set aside to cool. Store in an airtight container in the fridge for up to 1 month.