01 -
Peel and dice (or slice) the onions. Heat oil in a large heavy-bottomed pot over medium-high heat. Once hot, add the onions and cook for 15 minutes, stirring frequently, until tender and golden-brown.
02 -
Reduce heat to low, add the thyme sprigs and bay leaf, and cook for 3-5 minutes to infuse flavors.
03 -
Sprinkle sugar evenly over the onions without stirring, and let it cook undisturbed for 5 minutes to melt properly. Increase heat to high and cook for another 5 minutes until the sugar caramelizes to a golden-brown color, monitoring closely to prevent burning.
04 -
Add the balsamic vinegar and stir to incorporate. Simmer on low heat for 5 minutes until mixture thickens. The jam is ready when a spoon drawn across the bottom of the pan leaves a clear trail for several seconds.
05 -
Remove the thyme sprigs and bay leaf, taste and adjust seasoning if necessary. Allow the jam to cool completely before transferring to a sterilized jar for storage.