How to Make It
Prepare the Cornbread: Place a 10-inch cast-iron skillet in oven. Preheat oven to 450°F. (Leave skillet in oven as it heats.)
Stir together cornmeal, flour, baking powder, baking soda, and salt in a large bowl. Whisk together buttermilk, oil, and eggs in a medium bowl. Add buttermilk mixture to cornmeal mixture; stir until combined. Carefully add butter to hot skillet. Return skillet to oven; bake until butter melts and lightly browns, about 1 minute. Carefully add melted butter to batter, and stir to combine. Immediately pour batter into hot skillet. Bake at 450°F until lightly browned and a wooden pick inserted in center comes out clean, about 20 minutes. Invert onto a wire rack; cool completely, about 30 minutes.
Prepare the Dressing: Reduce oven temperature to 375°F. Melt butter in a large skillet over medium. Add onion and celery. Cook, stirring occasionally, until tender, 12 to 14 minutes. Stir in thyme, sage, salt, and pepper. Cook until fragrant, about 2 minutes. Remove skillet from heat; cool 15 minutes.
Crumble Cornbread into a large bowl. Stir in onion mixture, stock, parsley, and eggs. Fold in pecans. Spoon mixture into a greased (with cooking spray) 13- x 9-inch baking dish. Bake at 375°F until top is lightly browned and Dressing is set, 30 to 35 minutes. Cool 10 minutes before serving.