Preheat oven to 350 degrees Fahrenheit. Melt the butter in a large skillet over medium heat. Add the onions and cook, stirring frequently until caramelized about 20 minutes. While onions are cooking add the corn muffins to a large mixing bowl.
Add sage with the onions cook for a minute then scrape into the bowl with the corn muffins. Season well with salt and pepper. Mix well until combined.
If mixture looks a bit dry, add a bit more chicken broth.
Frequently stir the caramelized onions so that they don't burn.
Once the stuffing is almost done about 10 minutes before it's done. I like to pick it out with a fork then finish baking. Picking the stuffing out keeps it from looking flat and helps achieve the slight craggy texture.
Make in advance tips:
Make the cornbread for your dressing up to two days before you are ready to make your dressing.
Refrigerator: Add your uncooked stuffing to an airtight container. Place it into your refrigerator for up to two days.
Freezer: Add your uncooked stuffing to an airtight container. Place it into your freezer. Thaw uncooked stuffing for up to two days in the refrigerator.
Leftovers: To use cooked stuffing later, cool in shallow containers and refrigerate it within 2 hours. Use it within 3 to 4 days. Reheat leftover stuffing to 165 degrees Fahrenheit.