CARAMELIZE THE ONIONS:
In a large saute pan, heat one tablespoon of cooking oil over high heat. Add the onions and stir for 5-10 seconds. Leave the pan alone for about 1-2 minutes, or until the onions are starting to brown. When some of the onions are dark brown, add 1 Tbsp of water to stop the burning process. Let the water evaporate and stir the onions in order to get a uniform color on all the onions. Repeat this process 3-4 times. Finally, add in the balsamic or sherry vinegar and let it reduce until there isn’t any more liquid at the bottom of the pan. Cool the onions. These can be made up to 3 weeks ahead of time and stored in the refrigerator.
MAKE THE DIP:
In a medium-size bowl, combine all of the other ingredients except the chives. Add in the cooled caramelized onions. Transfer to a serving bowl and garnish with the chives.