Preheat oven to 400 degrees.
In large bowl, thoroughly combine crumbled cornbread, crumbled biscuits and shredded chicken. Set aside.
In medium sized saucepan, combine chicken broth, condensed cream of mushroom soup, condensed cream of chicken soup, and onions. Simmer over medium-low heat for 5 minutes. Stir constantly. NOTE: If using Homemade Cream of Chicken Soup, the amount is 1-1/4 cups.
Pour warm mixture over bread crumbs and chicken. Add 3 tablespoons of evaporated milk, beaten eggs, ground sage, ground black pepper, salt, and chopped celery (if using).
Stir until thoroughly combined. Set aside.
Generously grease 12-cup bundt pan with shortening. Do not use vegetable oil because the crust will stick to the pan.
Place greased bundt pan in preheated HOT oven for 5 minutes OR until shortening sizzles. Preheating helps crust to thoroughly bake.
Carefully remove HOT bundt pan from oven. Pour in batter. Return to HOT oven.
Reduce oven temperature to 375. Bake 20-25 minutes OR until edges turn "dark brown" and knife inserted in center comes out clean.
Remove from oven. Cool at least 10 minutes. Place plate on top of bundt pan. Flip over. Tap to release.
Bundt shape should be firm and outside should be crusty. Garnish by placing a small bowl of cranberry sauce in center (optional).
Slice with a serrated knife.
Do not pour hot gravy or chicken stock over Cornbread Bundt Dressing because liquids will soften the shape and cause it to slump.
Drizzle each warm or hot serving with hot gravy or chicken stock.