01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish with butter.
02 - In a large skillet over medium heat, cook the sausage until browned, breaking it apart with a spoon, about 6-8 minutes. Transfer the sausage to a plate, leaving any drippings in the pan.
03 - Add the diced onion and celery to the skillet with the remaining drippings. Sauté until softened, about 5 minutes. Remove from heat and set aside.
04 - In a large mixing bowl, combine the bread cubes, cooked sausage, sautéed onion and celery, dried cranberries, chopped parsley, dried sage, dried thyme, salt, and black pepper. Toss until evenly distributed.
05 - In a separate bowl, whisk together the eggs, whole milk, heavy cream, and melted butter until smooth and fully incorporated.
06 - Pour the egg custard over the bread mixture and toss until everything is well coated. Fold in the shredded cheddar cheese. Transfer the mixture to the prepared baking dish, spreading it into an even layer. At this stage, the assembled casserole can be covered and refrigerated overnight if preparing ahead.
07 - Bake uncovered for 45-50 minutes, or until the top is golden brown and the custard is fully set in the center when tested with a knife.
08 - Remove from the oven and let the casserole rest for 10 minutes before slicing and serving. Garnish with additional fresh parsley if desired.