In a skillet over medium heat, melt the butter or olive oil.

Add the sliced onions and cook until they are soft and caramelized, about 45 minutes.

Stir in the minced garlic and cook for an additional minute.

In a mixing bowl, combine the cooked onion and garlic mixture with sour cream, mayonnaise, chives, parsley, salt, and pepper.

Adjust seasoning to taste, adding Worcestershire sauce if desired.

Serve chilled or at room temperature.