Preheat the oven to 450°. Put the butter in a 10-inch cast-iron skillet and melt the butter in the oven. Meanwhile, in a large bowl, mix the cornmeal with the cream of tartar, salt and baking soda. Add the buttermilk and eggs and stir to blend. Remove the skillet from the oven and swirl to coat with the butter. Pour the melted butter into the batter and stir just until incorporated. Scrape the batter into the hot skillet and bake for about 35 minutes, or until crusty around the edge and springy to the touch. Invert the cornbread onto a rack and let cool completely.
Break the cornbread into large pieces, scatter on a baking sheet and let dry overnight.
Preheat the oven to 400°. On a rimmed baking sheet, toast the pecans for about 10 minutes, or until nicely browned and fragrant. Transfer to a plate to cool. Reduce the oven temperature to 325°.
In a large skillet, cook the bacon in 6 tablespoons of the butter until very crisp, about 10 minutes; reserve the bacon for another use. Add the onions, celery, shallots, sage and thyme to the skillet and cook over low heat until the vegetables are tender, about 25 minutes.
Tear the cornbread into 1 1/2 -inch pieces and place in a large bowl. Top with the cooked vegetable mixture and the pecans and toss well. Stir in the 4 tbs melted butter, the eggs and 1 cup of the chicken stock. Season with 1 1/2 teaspoons of salt and 1 teaspoon of pepper and mix well.
Butter a large shallow baking dish and add the cornbread dressing. Cover with foil and bake for 30 minutes. Uncover and baste the dressing with 6 tablespoons of the remaining stock. Bake for 10 minutes longer, then baste with the remaining 6 tablespoons of stock. Bake for 20 minutes longer, or until golden brown on top and heated through.