In a large bowl mix all ingredients except the egg. Mix well and give it a taste. Add more salt, pepper or sage if extra seasoning is needed. This will depend a lot on the type of broth you use.
Add the beaten egg once the seasoning is good and mix well.
Transfer the mixture to a greased 2.5 quart casserole dish and bake until hot in the center and the bread is starting to get golden on top; 20-25 minutes. Keep an eye on it and cover with foil for the last few minutes of baking if it gets too dark.
Notes
Note 1: If you don't want to use cornbread, just add in 4 cups more of the crusty bread of your choice. Brioche, sourdough or an artisan boule are all great options. Note 2: Leave both your cornbread and other bread out to dry for about two days if possible. Slice the bread and leave it on a plate covered with a cloth. Cube it or crumble after it dries out. Note 3: If using dried sage, use 2-3 teaspoons. Taste as you go until the flavor is obvious but not overwhelming. Note 4: Chicken broth can vary widely in saltiness. Avoid bouillon cubes or powders at all cost and try to buy one that has at least some flavor. I like Pacific Foods or Kettle and Fire chicken broth (not bone broth). Making your own broth is always best.