Notes: The cornbread (homemade or from a 13-oz. mix) can be baked up to 1 day before preparing dressing. If you especially like mustard greens, use two packages. Prepare dressing through step 4 up to 1 day ahead; cover and chill. Heat, covered, in a microwave-safe container in a microwave oven on full power (100%), stirring occasionally, until hot in the center, 5 to 6 minutes. Or bake, covered, as directed in step 5 until hot, 50 to 60 minutes, then uncover to brown as directed.
7 to 8 cups 1/2-inch cubes cornbread (see notes)
1 cup coarsely chopped pecans
2 tablespoons butter or margarine
6 ounces cooked ham, cut into 1/4-inch dice
1 onion (12 oz.), peeled and chopped
1 cup chopped celery
1 or 2 bags (1 lb. each) frozen chopped mustard greens, thawed (see notes)
Spread cornbread cubes in a 12- by 17-inch roasting pan. Bake in a 350° regular or convection oven, stirring occasionally, until edges begin to brown, 25 to 35 minutes. Spread pecans in a 9-inch pie pan and bake in same oven until lightly browned, about 10 minutes.
In a 5- to 6-quart pan over medium-high heat, melt butter; add ham, onion, and celery and stir often until onion begins to brown, 7 to 10 minutes.
Squeeze excess liquid from mustard greens. Stir greens, corn, and sage into ham mixture. Mix in cornbread and enough broth to moisten lightly. Stir in pecans.
Spoon dressing into a shallow 3-quart baking dish and cover tightly.
Bake in a 325° regular or convection oven (350° if baking with a turkey at that temperature) until hot in the center, 15 to 25 minutes. Uncover and bake until top is lightly browned, 15 to 25 minutes longer. Add salt and pepper to taste.