Heat 1 tablespoon oil in a medium skillet over medium-low heat. Add the onions and 1/2 teaspoon salt, and cook until soft and just starting to brown, about 4 minutes. Add the corn, and cook, stirring, until heated through and starting to turn golden, about 3 minutes. Add the remaining 1 tablespoon oil and the garlic, and cook until fragrant, about 2 minutes. Set aside 1/2 cup of the vegetable mixture. Transfer the rest to a food processor, add 1/4 cup water and process until mostly creamy with a little texture.
In a medium bowl, combine the sour cream, mayonnaise, parsley, Parmesan, 1/2 teaspoon salt and 1/4 teaspoon pepper. Add the pureed vegetables and the reserved mixture, and stir to combine. Refrigerate, covered, for at least 1 hour up to 3 days before serving. Serve chilled, with dippers.
Copyright 2016 Television Food Network, G.P. All rights reserved.