To lightly toast the bread, place on a baking sheet and toast in the oven at 210°F/100°C for 90 minutes, flipping every 30 minutes. This can be done a few days ahead.
Preheat the oven to 350°F/180°C.
In a medium skillet, over medium heat, melt 1 tablespoon of butter and cook the sausage meat until It’s done and no longer pink (about 5-7 minutes). Break it up with a wooden spoon as you cook it.
Add the rest of the butter, melt it and saute the onion and celery until tender (not brown). Add the garlic, and cook for a minute or until it's fragrant then remove from heat.
In a large mixing bowl, combine the toasted bread with the sausage mixture, and chopped herbs. Season with salt and pepper. Add a cup of stock, and mix everything with a spatula or your hands.
Combine beaten eggs with the remaining stock or broth, and add it gradually to the bread. Keep mixing and make sure that the bread is soaked all the way through but not mushy.
Transfer to a 13 x 9-inch baking pan, cover with foil, and bake for 35-45 minutes or until an instant read thermometer registers 160°F/71°C in the center of the stuffing. Uncover and brown the top for 10 minutes or until it's golden and crispy.
Garnish with additional chopped parsley and serve.