In a large skillet over high heat, melt the butter. Add in the carrot, onion, and celery and cook, stirring often, until soft, 2-3 minutes, and transfer them to a large bowl.
To the same bowl, add the meatballs, stock, oil, parsley, rosemary, sage, bread, salt & pepper. Stir everything until well mixed. Spread the stuffing mixture out evenly into a large cast iron skillet or into a 9" x 13" baking dish.
Bake at 450 degrees, or until golden brown and bread is slightly crisp on top, 15-20 minutes.
Sprinkle with chopped fresh parsley before serving.