Preheat oven to 350°F. Grease a 9 x 13-inch baking dish or spray with nonstick cooking spray; set aside.
In a large bowl, whisk or stir together cheddar cheese, sour cream, condensed soups, ½ cup of the melted butter, and the black pepper. Fold in the chicken, thawed shredded potatoes, and pimentos. Taste and season with salt, if necessary. Transfer the mixture to the prepared baking dish.
Prepare the topping for the casserole by combining the crushed Corn Flakes with the remaining 2 tablespoons of melted butter. Sprinkle on top of the potato mixture.
Bake, uncovered, until the filling is hot and bubbly and the topping is browned, about 40-45 minutes.
