Brown sausage in a large skillet over medium-high heat, breaking it into pieces as it cooks. once no longer pink, remove sausage from skillet with a slotted spoon and place in a large bowl.
Add butter to grease in skillet and cook celery and onion until soft, about 5 minutes.
Add sage, thyme, and parsley to skillet and season onion/celery mixture with salt and pepper. Add mixture to bowl with sausage.
Add toast pieces and crumbled cornbread to bowl. Stir to combine.
Add eggs, 2 cups broth, salt and pepper and stir well. Add up to 1 cup more chicken broth to get mixture very moist.
Transfer mixture to a greased 6-quart slow cooker.
Scatter butter pieces on top.
Cover and cook on LOW for 3 to 4 hours.