Preheat your oven to 400°F if you plan to bake immediately.
In a large skillet over medium heat, melt the 6 tablespoons of butter. Add the chopped onion and celery, and sauté until softened and translucent, about 7 to 8 minutes. Remove from heat and allow the mixture to cool slightly.
Place the crumbled cornbread in a large mixing bowl. Add the sautéed onion and celery mixture, along with the chopped herbs, salt, and pepper. Stir until everything is well combined. Gradually pour in ½ cup of chicken broth to start, adding up to a full cup if needed to keep the dressing slightly moist. (If making the dressing in advance, use just ½ cup of broth at this stage, reserving the rest to add before baking.)
Transfer the cornbread mixture into a greased 9x13-inch baking dish or a 3-quart casserole dish. Dot the top with the cubed butter. Drizzle extra broth on top if needed to maintain moisture (skip this step if you’re preparing the dish ahead). If prepping in advance, cover the dish tightly with plastic wrap and refrigerate for up to one day.
Bake the dressing at 400°F for 35 to 40 minutes, or until it’s golden and set. Allow it to rest for 5 to 10 minutes before slicing, giving the dressing time to firm up. Serve hot and enjoy!