Heat oven to 325℉.
In large skillet over medium heat, melt ¼ cup butter. Once melted, add 3 cups chopped onions, 2½ cups chopped celery, 1 finely minced garlic clove, 1½ tablespoons chopped fresh sage, 1½ tablespoons chopped fresh thyme, 2 teaspoons celery seeds, 1 pinch grated nutmeg, and 1 teaspoon kosher salt. Mix well.
Cover and cook 5 to 7 minutes or until onions are soft. Remove from heat.
In a large bowl, toss vegetables, cubed bread, and ½ teaspoon pepper. Set aside.
Melt ¼ cup remaining butter. Once melted, add 1½ cups chicken broth. Mix well and pour over stuffing mix. Toss to coat.
Cover stuffing. Bake about 35 minutes or until stuffing is warmed through.
Uncover and bake for an additional 15 minutes.