Cube your bread and spread it out on a baking sheet. Leave uncovered overnight to dry out. ALTERNATIVELY if you don't have time to do the day before, place in a 225 degree oven for 30-40 min. Place in a 9x13 casserole dish and set aside.
Preheat oven to 350°
In a large pan/pot, melt butter and add in chopped onions, celery, and garlic and saute for 5 minutes, or until veggies are tender
Add in pork sausage and break it up into chunks with a wooden spoon. Cook until no longer pink.
Stir in chopped herbs and season with salt and pepper to taste. Continue cooking 3-4 minutes to cook out raw herb taste.
Remove from heat and pour in chicken stock and beaten egg. Stir immediately to avoid scrambling.
Pour contents over bread and mix to combine. Press gently to flatten.
Bake for 35-40 minutes, or until the top is golden brown and the inside is moist but not wet. Allow to set for 5 minutes then serve.