Caramelized Onion Preserves

4 pounds onions
4 tablespoons olive oil
1.5 cups sugar
1.5 cups balsamic vinegar
fresh thyme sprigs
fresh rosemary sprigs
2 teaspoons canning salt

Slice the onions and place them in a stockpot with the olive oil. Cook the onions over medium heat until they are golden and translucent. Add sugar, vinegar, and sprigs. Cook down to a syrup. Will take about an hour.

Remove the sprigs and stir in the canning salt. Ladle the mixture into sterile jars, leaving 1/4 inch of headspace. Remove any air—place on lid and ring, Place in canner for 15 minutes. Remove and let cool overnight.