Preheat the oven to 350 degrees and cook potatoes.
Once the cooked potatoes are cool enough to handle, peel them and place them in a large mixing bowl.
Coarsely mash the potatoes with ½ cup of the milk.
Cut the bread into ½-inch diced cubes
Place them in a small mixing bowl and pour the remaining milk over them.
Soak for several minutes. In the meantime, heat the oil in a medium-sized skillet.
Add the onion and celery and sauté over low heat until the onion is lightly browned and the celery is tender.
Combine the onion and celery mixture with the mashed potatoes in the large mixing bowl.
Stir in the soaked bread, parsley, and seasoning mix.
Season to taste with salt and lots of pepper.
Pour the mixture into a well-oiled, 2-quart baking dish.
Bake for 50 to 60 minutes, or until the top is a crusty golden brown.