Bake cornbread mix according to package directions. In a large bowl, crumble cooled cornbread (about 7 cups).
Reduce oven temperature to 350°F. Spray an 11x7-inch baking dish with nonstick cooking spray. In a small nonstick skillet, melt 1 Tablespoon butter over medium-high heat. Add celery, and cook, stirring often, 3 minutes, or until soft; add to crumbled cornbread. Melt remaining 1 tablespoon butter in skillet; add shallots and garlic, and cook, stirring often, 2 to 3 minutes, or until translucent. Add to cornbread mixture.
Add cranberries, walnuts, parsley herb blend, and poultry seasoning to cornbread mixture; stir well. Add chicken broth, milk, and egg, stirring until thoroughly combined. Pour mixture into prepared baking dish.
Bake at 350°F for 35 to 40 minutes, or until center is set.