Place 1/2 cup butter in a 13- x 9-inch pan; heat in oven at 425° for 4 minutes.
Stir together cornmeal and flour; whisk in 3 eggs and buttermilk.
Pour hot butter into batter, and stir until blended. Pour batter into pan.
Bake at 425° for 30 minutes or until golden brown. Cool. Crumble cornbread into a large bowl; stir in breadcrumbs, and set aside.
Melt remaining 1/2 cup butter in a skillet over medium heat; add onions and celery, and sauté 5 minutes. Stir in sage, parsley, and seasoned pepper; sauté 1 minute. Remove from heat, and stir into cornbread mixture.
Whisk together chicken broth and remaining 4 eggs; stir into cornbread mixture. Pour evenly into 1 lightly greased 13- x 9-inch pan and 1 lightly greased 8-inch square pan.
Bake at 400° for 35 to 40 minutes or until golden brown.
Note: For testing purposes only, we used White Lily Self-Rising Buttermilk Cornmeal Mix.