Melt butter in heated large skillet over medium high heat; saute onions, celery and fennel until browned about 12 minutes. Add sausage and garlic; cook 5 minutes. Stir in salt, thyme, pepper and bay leaves and cook 3 minutes.
Meanwhile, if challah is not stale, spread out cubes in baking sheet and dry out in 250 oven about 30 minutes, stirring once.
Combine sausage vegetable mixture with bread and add chicken broth as needed to make a moist but not soggy mixture.
Fill a 16 lb prepared turkey with stuffing. Cook turkey as directed. Otherwise place stuffing in a roasting pan; cover and bake 350 about an hour until done. Uncover for last 10 minutes.