Preheat oven to 250° F. Rip bread and croissants into 1 inch sized pieces and and scatter them in a single layer on a rimmed baking sheet. Bake the pieces, stirring occasionally, until dried out, about 1 hour. Let them cool, then transfer to a very large bowl.
After making the croissant and bread croutons, chop the celery, scallions, and onions. Set aside the dark green ends of the scallions for later. Meanwhile, melt 3/4 cup butter in a large skillet over medium-high heat; add the whites of the scallions, chopped onions, and celery. Stir often until just beginning to brown, about 10 minutes.
Stir in all of the herbs to the celery mix and then remove the pan from heat. Add this entire mixture to the large bowl of croissants and bread pieces. Sprinkle in salt and pepper, then drizzle in 1 ¼ cups of broth and toss gently.
Preheat oven to 350° and butter a 9x13 baking dish. Whisk in the remaining 1 ¼ cups broth and eggs in a small bowl. Add to stuffing mixture; fold gently until thoroughly combined. Transfer the mix into a buttered 9x13 baking dish, cover loosely with foil, and bake about 40 minutes..
Remove the foil and continue to bake, uncovered, for another 40 minutes or until the stuffing looks set and does not appear wet. The tops should appear crispy and golden brown all around.
Once the stuffing is complete and ready to serve, sprinkle the chopped green ends of the scallions on top for garnish.
Do Ahead: Up to 3 days ahead of time, follow steps 1-4, cover the stuffing, and store in the fridge. On the day of serving, uncover and follow step 5 and serve.