Cut and dry the bread: Dice your day-old French bread into 1/2-inch cubes and spread them on a large baking sheet. Bake at 300°F for 15 minutes, stirring halfway through, until the bread is lightly toasted and completely dried out. This prevents soggy stuffing.
Cool completely: Remove the toasted bread cubes from the oven and let them cool for 5 minutes before proceeding. Set them aside in a large mixing bowl.
Sauté the aromatics: In a large skillet, melt 1/2 cup of butter over medium heat. Add the diced onion and celery, cooking for 8-10 minutes, stirring occasionally, until the vegetables are soft and fragrant. The onions should turn translucent and slightly golden.
Add the fresh herbs: Stir in the minced sage, rosemary, thyme, and parsley. Cook for 2 minutes, allowing the herbs to release their oils and perfume the butter. This step creates incredible depth of flavor.
Combine with bread: Pour the herb-butter mixture over the cooled bread cubes and toss gently but thoroughly, ensuring every piece is coated.
Whisk the eggs: In a small bowl, beat the 2 large eggs until well combined. In a separate bowl, warm 2 cups of the chicken broth gently over low heat, about 2-3 minutes.
Temper the eggs: Slowly pour the warm broth into the beaten eggs while whisking constantly, then add the remaining 1/2 cup of cold broth. This prevents the eggs from scrambling and creates a smooth liquid base.
Pour over bread: Drizzle the egg and broth mixture over the bread and herb combination, folding gently with a wooden spoon until everything is moistened evenly. The mixture should be wet but not soggy, with bread pieces still holding their shape.
Prepare the baking dish: Butter a 9 x 13-inch baking dish thoroughly with the remaining 1/2 cup of butter, coating the bottom and sides generously. This prevents sticking and adds extra richness.
Transfer the mixture: Spoon the stuffing into the prepared dish, spreading it into an even layer. Press down gently with the back of a spoon, but do not compact it too firmly, as the stuffing should stay light and fluffy.
Bake: Cover the dish tightly with aluminum foil and bake at 350°F for 30-35 minutes, until heated through. Remove the foil and bake uncovered for an additional 10-15 minutes, until the top is golden brown and slightly crispy.