In a food processor, add the cream cheese, mayo, and sour cream. Pulse to combine. Add the caramelized onions and pulse a couple of times to mix, but do not break up the onions too much. Taste, and season with salt and pepper.
Transfer to a bowl and cover. Refrigerate about 2 hours or until ready to serve. Serve with chips and vegetable sticks. Dip will keep covered in the refrigerator for 3 days.
Recipe by Work. Cook. Eat. at https://www.workcookeat.com/french-onion-dip/