In a mixing bowl, combine 3 cups of crushed cornflakes with 4 tablespoons of melted unsalted butter, stirring until the cornflakes are evenly coated. Set this mixture aside for later use.

Using a large sauté pan, melt the remaining 4 tablespoons of unsalted butter over low heat. Add 1 cup of sliced green onions and sauté gently for about 5 minutes until soft and fragrant.

Sprinkle ¼ cup of all-purpose flour, along with salt and pepper to taste, over the softened onions. Gradually pour in 1 cup of heavy whipping cream and ½ cup of half-and-half, stirring continuously until the mixture thickens and starts to bubble.

Remove the sauce from heat and stir in 2 cups of shredded sharp cheddar cheese, mixing until it melts completely. Fold in 3 cups of cooked and drained crinkle-cut carrots along with 2 tablespoons of parsley flakes.

Preheat your oven to 350°F (175°C) and grease a 9 x 13-inch baking dish. Pour the carrot and cheese mixture into the prepared dish, spreading it evenly. Sprinkle over the reserved cornflake topping.

Cover the baking dish with aluminum foil and place it in the preheated oven. Bake for approximately 40 minutes, then carefully remove the foil and continue baking for an additional 5 minutes until the top is golden brown and crisp.