Heat the oven to 300 degrees. Place the bread cubes and crumbled cornbread in a shallow roasting pan or on a cookie sheet. Toast the bread for 10 minutes. Set aside.
Heat the butter or olive oil over low heat in a large sauté pan. Sweat the onions, carrots, celery, mushrooms and garlic until tender. Season with salt and pepper.
In a large bowl, combine the breads, vegetables, sage and pecans. Add enough chicken stock to moisten the bread without making it too soggy. Season with salt and pepper.
Use this mixture to stuff a turkey, or bake in an ovenproof dish for 30 minutes.