Heat the butter and olive oil in a large skillet over medium-low heat. Once the pan is hot, add the onions and cook until the onions are nice and caramelized, about 25 minutes. Add the sherry and garlic and cook for an additional 10 minutes.
In a large mixing bowl, combine the cream cheese, sour cream, and parmesan. Mix until all ingredients are well incorporated. Set aside come of the caramelized onions and bacon for the top of the dip.
Add the remaining caramelized onions, bacon, and parsley to the bowl and mix until well combined.
Top with remaining onions and bacon.
Serve as is, or transfer to a baking dish and bake at 325°F for 20 minutes.
Serve with your favorite low carb dippers – celery, sliced bell peppers, cucumber, pork rinds etc.