Preheat the oven to 350°F
You'll want to cook the sausage first then place it to the side. While the sausage is cooking dice the onion and mince the celery stalk and chop up the fresh parsley.
In the same pan you cooked the sausage in add a little oil and sauté the onions and minced celery. Cook until softened and fragrant then add in the minced garlic. Continue cooking for another 3 minutes or so then right before turning off the heat add in the chopped parsley.
In a mixing bowl combine the bread, sausage and the sautéed veggies you just cooked.
Pour 1 cup of chicken stock/broth and beat 1 egg into it. Then pour it in the mixing bowl over the stuffing ingredients. Mix well until most of the liquid is absorbed by the bread.
In a 8x8 casserole dish pour the contents in there and pat down evenly with the back of a spoon.
Cube the 3 TB of butter and place all over the top of the stuffing. Then cover with aluminum foil.
Place in oven for 30 minutes covered then remove the cover and bake a remaining 20 minutes. For a crispy top you can broil the recipe for a few minutes at the end.
Allow to cool a bit then serve