Preheat oven to 350°F. Butter the baking dish and set aside.
In a large skillet over medium heat melt the butter and then add the celery and onion. Sauté for about 5 to 6 minutes or until celery and onions are tender. Season with salt, pepper, and poultry seasoning.
Tear the sandwich bread into 1-½ inch pieces and place in a large bowl, keeping it as uniform as possible.
Stir in the sautéed celery and onion mixture, salt, pepper, and poultry seasoning, then stir until well blended.
Add half the broth a then work the mixture until you get a well-combined but lumpy dressing. Add the remaining broth and combine well.
Add the heavy cream, stirring one more time. The dressing should be broken down and wet but there should be no standing liquid. Add the parsley and taste for additional salt or poultry seasoning.
Transfer the dressing to a greased baking dish. Bake for 45-60 minutes or until dressing is browned and cooked through.