The day before making the stuffing, bake the cornbread: Preheat oven to 450°F. Melt 2 tablespoons butter in cast iron skillet over medium heat. Combine cornmeal, flour, baking powder, baking soda and salt in a large mixing bowl.
In a separate bowl whisk buttermilk, milk and egg until combined. Slowly incorporate the wet ingredients into the dry, until just combined. A few lumps are okay.
Add the melted butter and stir gently until just combined. Pour batter into hot skillet and bake in pre-heated oven for 20 – 25 minutes or until a toothpick comes out with few crumbs attached.
Let cool in the skillet and then cut into 1 inch cubes or smaller to taste.
Spread cornbread and French bread cubes onto two baking sheets and dry over night (~24 hours) at room temperature until they are crisp.
Dump into large bowl and toss to mix.
For the Stuffing:
Preheat oven to 350°F. Melt the butter in a large skillet or Dutch oven over medium heat.
Add celery, carrots, and onion and cook until onion is almost translucent. Add chicken broth and bring to a boil. Reduce heat to low and add the spices. Taste and add a little salt as desired.
Gradually ladle the hot broth mixture into the bowl with the bread, tossing gently. If the mixture is not moist enough, add more broth. Stir in parsley.
Transfer mixture to a 9x13 inch baking dish. I used the same cast iron skillet that I used above. Bake until golden brown, 20 to 25 minutes. Let rest 10 minutes prior to serving.