01 - Preheat oven to 350°F. Grease a 9x13-inch baking dish generously with butter.
02 - In a large skillet over medium heat, cook the sausage until browned throughout, breaking it apart with a spoon into crumbles, about 6 to 8 minutes. Transfer the sausage to a plate using a slotted spoon, leaving any rendered drippings in the pan.
03 - Add the diced onion and celery to the same skillet with the drippings. Sauté over medium heat until softened and translucent, about 5 minutes. Remove from heat and set aside.
04 - In a large mixing bowl, combine the bread cubes, browned sausage, sautéed onion and celery, dried cranberries, chopped parsley, dried sage, dried thyme, salt, and black pepper. Toss until all ingredients are evenly distributed.
05 - In a separate bowl, whisk together the eggs, whole milk, heavy cream, and melted butter until smooth and well blended.
06 - Pour the egg custard mixture over the bread and filling mixture. Toss gently until every bread cube is thoroughly coated. Fold in the shredded cheddar cheese. Transfer the entire mixture to the prepared baking dish, spreading it into an even layer. At this stage, the dish can be covered and refrigerated overnight if preparing ahead.
07 - Bake uncovered for 45 to 50 minutes, or until the top is golden brown and the egg 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.