Preheat the oven to 350°F. Grease a 13x9-inch baking dish with unsalted butter then set it aside.
Add the butter to a large skillet set over medium-low heat. Once the butter has melted, add the onions, celery, garlic, 1 teaspoon kosher salt an 1/2 teaspoon black pepper and cook, stirring, until the vegetables have softened, 5 to 7 minutes. Transfer the mixture into a very large bowl.
To the bowl with the vegetables, stir in the rosemary, sage, thyme and 1 cup of the chicken broth.
Add the bread cubes to the bowl and toss gently.
In a separate medium bowl, whisk together the remaining 1 1/2 cups chicken broth with the eggs. Pour the mixture over the bread and stir until well-combined.
Transfer the stuffing into the greased baking dish, cover it with foil and bake until it reaches an internal temperature of 160°F, about 45 minutes.
Uncover the stuffing and continue baking until the top is golden brown and slightly crisped, 15 to 20 minutes.
Let cool slightly before serving or let cool completely before covering and storing in the fridge until ready to eat.