Place 1/2 cup butter in a 13" x 9" pan; heat in oven at 425° for 4 minutes.
Combine cornmeal and next 5 ingredients; whisk in 3 eggs and buttermilk.
Pour hot butter into batter, stirring until blended. Pour batter into pan.
Bake, uncovered, 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 onion and celery, and sauté until tender. Stir in sage; sauté 1 minute. Stir vegetables, remaining 4 eggs, chicken broth, and pepper into cornbread mixture. Shape unbaked dressing into croquettes, using a 1/4 cup ice cream scoop. Place croquettes on lightly greased baking sheets, making sure not to crowd them on the sheets.
Bake at 400° for 30 minutes or until well browned (and internal temperature reaches 160°). Cool on baking sheets 10 minutes.