Heat the oven to 325 F.
Heat a grill pan over high and cook the corn until charred on all sides, 15 minutes
Cut the kernels from the cob, and purée two-thirds of the kernels in a food processor with the cream, ricotta, flour, and thyme. Season with salt and pepper and stir in remaining kernels.
Scrape the dip into an 8-inch baking dish, sprinkle with parmesan and dot with butter. Bake until bubbly, about 1 ½ hours.
Garnish with chives and scallions to serve.