In a large skillet, heat the olive oil and butter over medium heat.
Add the sliced onions, salt, and sugar. Stir to combine.
Cook the onions, stirring occasionally, for about 25-30 minutes, or until they are golden brown and caramelized.
Once caramelized, remove the skillet from heat and let the onions cool slightly.
In a mixing bowl, combine the sour cream, mayonnaise, Worcestershire sauce, garlic powder, and black pepper. Mix until smooth.
Fold in the cooled caramelized onions and chives, if using.
Transfer the dip to a serving bowl and refrigerate for at least 1 hour to allow the flavors to meld.
Serve with fresh vegetables and chips.