Heat the oil in a medium pan set over medium heat. Add half of the red onions and the yellow onions, and saute, stirring, until caramelized, 20 minutes. Add the sherry and wine, and cook, stirring continually, until the liquid reduces completely. Refrigerate until completely cool, 15 to 30 minutes.
In a large bowl, add the chilled onions, reserved red onions, sour cream, salt, pepper and scallions. Serve at room temperature with kettle chips.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.