Heat the oven to 350° F. Spray a casserole dish with cooking spray. An 8x8" dish works great.
In a medium skillet over medium heat, brown the sausage until there is no more pink, about 5-7 minutes. Once the sausage is fully cooked, set it on a plate lined with paper towels to drain the excess grease.
While the sausage is cooking, combine the bread, parsley, sage, thyme, rosemary, and marjoram, and mix well. Set aside.
Using a small bowl or a measuring cup, combine the egg and chicken stock. Beat the egg into the chicken stock. Set this aside as well.
Once the sausage is fully cooked, leave whatever grease is in the pan and add the butter to the same skillet. Next, add the onions and celery. Season with salt and pepper and saute until soft, about 5 minutes. Add the garlic and cook for another 1-2 minutes.
Add the cooked sausage and cooked vegetables to the mixing bowl. Slowly pour in the chicken stock with egg mix into the bowl and stir gently. You can add a little, stir, add a little more, stir again, and so on. You want all the bread to get wet through with the chicken stock. You don't want any of it to be soggy or dry. I use a kitchen towel under the bowl to hold it still while I'm stirring.
Once everything is mixed, pour the stuffing into the casserole dish and cover with foil. Place it in the oven for 45-50 minutes.
If you would like the top a little more brown and crispy, bake for 30 minutes covered, then 20-30 minutes uncovered.
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