In a large skillet, heat butter and olive oil over medium heat. Add frozen diced onions and brown sugar. Cook the onions, stirring occasionally, until they are golden brown and caramelized, about 15-20 minutes.
Allow the caramelized onions to cool to room temperature.
In a mixing bowl, combine sour cream, mayonnaise, Worcestershire sauce, garlic powder, salt, and pepper.
Once the caramelised onions have cooled, stir them into the rest of the ingredients until well combined.
Cover the bowl and refrigerate the dip for at least 1-2 hours.
Before serving, garnish with fresh chives or green onions. Serve the caramelized onion dip with chips or bread.
