A few hours in advance, cut or tear the cornbread into pieces and leave out (we want it a little bit stale). Alternatively, leave a bowl of the cornbread out overnight, lightly covered.
When ready to prepare dressing, preheat oven to 375 degrees. Spray a 9x13 baking pan, or large casserole, with baking spray and set aside.
Heat 2 tablespoon olive oil in a large pot or Dutch oven. Add the onion and celery, stirring to coat. Cook until vegetables start to soften, about 3 minutes, stirring occasionally, before adding garlic and cooking until fragrant, about 1 more minute. Season with salt and pepper, to taste, and add the poultry seasoning, stirring to coat.
Add butter and stir until melted before adding stock. Cook until stock is heated through.
Meanwhile, combine dried cornbread and stuffing bread in a large bowl. Carefully pour the warm stock mixture over the bread pieces, reserving about 1 ½ cups. Gently toss to combine (being delicate will keep together big pieces of cornbread-y goodness!). Spoon dressing into prepared baking pan and pour some of the remaining stock over any areas that appear dry (if you don’t use it all, that’s ok!).
Cover with foil and bake in preheated oven for 20 minutes. Remove foil and bake for an additional 20 – 25 minutes, or until top of stuffing is golden brown and crisp. Serve warm alongside your favorite Thanksgiving meal!