Place the bone-in, skin-on chicken pieces into a large stockpot and season generously with salt and black pepper. Cover the meat completely with cold water, bring to a rolling boil over high heat, then immediately drop the flame to medium-low to maintain a gentle simmer until the chicken is tender to the core and pulls away easily from the bone.

Lift the cooked chicken out of the pot and transfer it to a clean platter to cool, leaving the hot, rich cooking broth inside the pot to use later. Once cool enough to handle, strip the meat from the framework, shred it into bite-sized pieces, and discard the skin and bones.

In a separate medium saucepan, combine the chopped yellow onion, chopped celery, and the 6 whole raw eggs. Cover the ingredients completely with cold water, bring to a rolling boil over high heat, and cook continuously for exactly 15 minutes.

Empty the pan into a colander to drain the water, then immediately shock the hot elements under ice-cold running water. Carefully peel the hard-boiled eggs and finely chop them along with the softened onion and celery pieces, setting the mixture aside.

Preheat your oven to 400°F and thoroughly grease a 9×13-inch baking dish with non-stick cooking spray or butter.

In an extra-large mixing bowl, combine the crumbled skillet cornbread and the torn white bread pieces. Measure exactly 4 cups of the warm chicken broth reserved from your stockpot and pour it directly over the bread solids, tossing gently until the liquids are completely absorbed into the starch matrix.

Add the shredded chicken, the chopped egg and vegetable mixture, poultry seasoning, dried sage, cream of chicken soup, salt, and black pepper directly into the moistened bread base. Fold the ingredients together from the bottom up until uniformly distributed; if the mixture feels dense or tight, stream in an additional 1 to 2 cups of the remaining chicken broth until it reaches a very wet, scoopable consistency.

Transfer the dressing mixture into your prepared 9×13-inch baking dish, using a spatula to smooth the surface into a flat, level sheet. Place uncovered on the middle oven rack and bake at 400°F for 45 minutes until the center is fully set and the shaggy top crown develops a beautiful, deep golden-brown crust. Let the dish rest on the counter for 10 minutes to allow the starches and protein binders to stabilize before spooning into deep bowls.