This recipe is adapted from one by Ina Garten that I found on the web. It's an easy recipe to make and goes very quickly.
2 large yellow onions
4 tablespoons unsalted butter (I used a little less)
1/4 cup vegetable oil (I used a little less)
1/4 teaspoon ground cayenne pepper
1 teaspoon kosher salt
1/2 teaspoon freshly ground black pepper
1 teaspoon Dijon mustard
1 teaspoon balsamic vinegar
4 ounces cream cheese, room temperature
1/2 cup sour cream
1/2 cup mayonnaise
Cut the onions in half and then slice them into 1/8-inch-thick half-rounds, about 3 cups total. (I quartered the onions).
Heat the oil and the butter in a large sauté pan over medium high heat. Add the onions, cayenne, salt and pepper and sauté for 10 minutes. Reduce the heat to medium low and continue to cook for 40 more minutes, stirring occasionally until the onions are browned and caramelized.
Add the Dijon mustard and balsamic vinegar and continue to cook for about 10 more minutes. Allow the onions to cool.
In a large bowl combine the cream cheese, sour cream and the mayonnaise. Whisk until smooth. Add all of the onions (I drained the onions of the excess oil before adding), reserving about a tablespoon for garnish, into the cream cheese mixture. Stir to combine and mix well.
Transfer to a serving dish and top with reserved onions. Refrigerate overnight to allow flavors to combine. Serve at room temperature with potato chips. (I used crackers. A french baguette would be good too).
Makes 2 cups