Heat the olive oil and butter over medium heat in a large, heavy-bottomed Dutch oven or large skillet.  When the butter is melted, add the onions and 2 teaspoons kosher salt, stirring to combine.  Cook the onions over medium heat, stirring occasionally, until the onions are softened but have not begun to color, about 15 minutes.  Lower the heat to medium-low and continue to cook, stirring occasionally, until the onions are a rich golden brown, another 45 to 50 minutes.  Cool the onions before adding to the dip mixture.

Mix together the cream cheese, crème fraîche and mayonnaise in a medium mixing bowl.  Season to taste with hot sauce, Worcestershire, salt and pepper.  Stir in the onions.  Garnish with the chopped chives.