Preheat the oven to 400 degrees F. Grease an 8x8 inch baking dish with butter or nonstick cooking spray.
In a large mixing bowl, add the 2 boxes of Jiffy corn muffin mix, 4 eggs, and ⅔ cup milk. Mix well and pour into the prepared baking dish. Bake for 18-20 minutes or until golden brown and baked through. If the cornbread is browning too quickly, cover it with aluminum foil while it bakes. Remove from the oven and let it cool.
While the cornbread cools, chop the onions and celery. Add the stick of butter to a large skillet. Add the onions and celery to the skillet and cook for 8-10 minutes over medium heat or until the vegetables are softened but not browned.
Chop the sage, parsley, and thyme. Add the fresh herbs to the vegetable mixture along with salt and pepper to taste. Mix and then turn off the heat.
Grease a 9x13 inch pan with butter or nonstick cooking spray.
Cut the white bread into cubes and add it to a large mixing bowl. Take the cornbread out of the baking dish and cut it into small pieces. Add the vegetables, herbs, and cornbread to the bowl with the white bread. Pour the chicken broth into the bowl and mix all the ingredients well. The cornbread will break apart, and that is ok! You want the stuffing to look wet, but not look soggy. 2-3 cups should be enough.
Pour the mixture into the prepared baking dish. Bake in the preheated oven for 15-20 minutes or until the top of the dressing is golden brown.