Preheat oven to 375 degrees F. Lightly grease a 9 x 13-inch baking dish; set aside.: Warmth from the oven ensures even baking and a crisp top as the stuffing heats through. You should feel a gentle, steady heat filling the oven and see the rack positioned to allow air circulation around the dish. Greasing the pan prevents sticking and helps the bottom brown evenly. A common mistake is skipping the preheat, which can lengthen bake time and produce uneven texture. If your oven runs hot or cool, an oven thermometer helps maintain accurate temperature.
Crumble the cornbread into a large bowl; set aside.: When you crumble the dried cornbread , notice the dusty, slightly crisp edges and the soft interior pieces; this mix of textures soaks up broth beautifully. Using your hands lets you control chunk size, aiming for a variety of pieces that create pockets of softness and crispness after baking. Avoid using fresh, wet cornbread because it will collapse into mush. If the cornbread feels too moist, let it air dry a bit more before using.
In a large skillet over medium heat, cook the sausage, breaking it apart as it cooks, until completely browned. Remove the sausage with a slotted spoon to a paper towel-lined plate.: As the sausage hits the pan you will hear a satisfying sizzle and smell a savory aroma as it browns. Break it into bite sized pieces so each morsel gets caramelized edges, which add flavor. Cooking until fully browned ensures fats render and flavor concentrates. A common error is crowding the pan, which causes steaming instead of browning. Use a large skillet and let the meat sit briefly between stirs to get good color.
In the same skillet, add the onion, celery and apple, and cook over medium heat until the onion is translucent and the celery and apple are softened, about 5 to 8 minutes. Remove from the heat.: The pan will now carry the fond from the sausage , and adding the onion , celery , and Granny Smith apple will deglaze those browned bits as they sweat. You want the onion to lose its raw edge and turn translucent, while the celery and apple become tender with a slight snap. The scent will shift from meaty to sweet and bright. Overcooking can make the apple disintegrate, so watch for softening without total collapse.
Add the sausage and cooked onion mixture to the bowl with the cornbread and stir to combine. Add the poultry seasoning, salt and pepper and stir to thoroughly combine. Add 2 cups of the chicken broth and stir until the mixture is evenly moistened. If it still seems a bit dry, add more broth a little at a time until the mixture appears damp.: Combining now lets the warm ingredients start to mingle, releasing steam that softens the cornbread subtly. The aroma of poultry seasoning , salt , and black pepper will bloom as you stir. When you pour the chicken broth , do so gradually, watching how the crumbs absorb liquid; the ideal feel is cohesive and damp but not soupy. Stopping to test ensures you avoid a watery consistency. A typical misstep is adding all the broth at once, which can swamp the bread and give a gummy texture.
Transfer the stuffing to the prepared baking dish, pressing it into an even layer. Drizzle with the melted butter and bake until the top is golden brown, 35 to 45 minutes. Leftover stuffing can be stored in an airtight container in the refrigerator for 3 to 4 days.: Pressing the mixture into an even layer helps it bake uniformly and develop a crisp top edge. As the dish warms you will hear a faint bubbling from pockets of broth and smell the butter toasting into a nutty aroma. The surface should turn an inviting golden brown, and the edges will firm up, creating contrast with the tender interior. Avoid opening the oven frequently, which cools and interrupts browning. If the top browns too quickly, tent a piece of foil to prevent overcoloring while allowing the interior to finish cooking.
Leftover stuffing can be stored in an airtight container in the refrigerator for 3 to 4 days: Once cooled, transfer extras into a sealed container to preserve texture and flavor. Chilling firms the stuffing, which makes reheating easier without becoming watery. When reheating, sprinkle a little chicken broth and warm gently to restore moisture. A common pitfall is leaving leftovers uncovered, which dries them out and dulls the flavors.