2 tablespoons unsalted butter, 2 tablespoons olive oil , 3 pounds yellow onions, cut in half lengthwise and crosswise into 1/4-inch slices, 2 tablespoons brown sugar , Salt and freshly ground pepper , 1/4 cup red wine vinegar , One 8-ounce package cream cheese, softened , 1 cup (8 ounces) sour cream , Chopped chives, for garnish, optional .
Heat the butter and olive oil in a heavy medium saucepan over medium-high heat. Add the onions and sugar. Cook, stirring constantly, until soft and golden brown, 15 to 20 minutes. Season with salt. Stir in the vinegar and simmer until the mixture is dry. Remove the mixture from the heat and allow the onions to cool slightly. Mix the cream cheese until smooth in a large bowl. Fold in the sour cream and caramelized onions. Season with salt and pepper. Garnish with chives if using. Can be eaten warm or transferred to the refrigerator to be eaten cold. Store in airtight container !!