At least one day in advance, cut the bread into cubes. Arrange on a baking sheet and allow to sit, uncovered, to dry out. Stale, dried out bread works the best!
On the day you’re going to make the stuffing, preheat the oven to 400 degrees Fahrenheit. Place the tray of bread in the oven for 10-15 minutes, or until the bread starts to brown.
Meanwhile, melt 5 tablespoons of butter in a large non-stick skillet. Sauté the onion and celery until soft and tender.
When the bread is toasted, transfer it to a large bowl. Add in the onion and celery mixture, chopped herbs, 3/4 teaspoon each of salt and black pepper, and 1 large egg, lightly beaten.
Add in 3 cups low-sodium chicken or turkey broth and stir to combine.
Spray a large 3 quart casserole dish with non-stick cooking spray. Transfer the stuffing mixture into the casserole dish. Cover with foil and bake for 30 minutes.
Remove the foil and bake for 10-20 minutes longer, or until the top of the stuffing starts to brown. Serve immediately.