For turkey: In a large stockpot, bring all ingredients and water to cover to a boil over high heat. Reduce heat, and simmer until turkey is cooked through, about 45 minutes. Remove from heat, and let stand for 30 minutes.
Remove turkey from broth, and let cool enough to handle. Shred meat, discarding skin and bones.
Strain broth through a fine-mesh sieve, discarding solids. Measure 5 cups broth for dressing; freeze remaining broth for another use.
Preheat oven to 350°. Spray a 13x9-inch baking dish with cooking spray.
For dressing: In a large skillet, melt butter over medium heat. Add onion, celery, and garlic; cook, stirring frequently, until very tender, about 10 minutes.
Crumble baked cornbread and biscuits into a large bowl; stir in cooked vegetables, shredded turkey, poultry seasoning, sage, and thyme. Stir in eggs. Gradually stir in reserved 5 cups broth just until dry ingredients are moistened. Spoon mixture into prepared pan.
Bake until center is set, 30 to 45 minutes. Let stand for 10 minutes before serving. Garnish with parsley and sage, if desired.
Recipe by Paula Deen Magazine at https://pauladeenmagazine.com/turkey-and-dressing-casserole-recipe/