Preheat the oven to 350 degrees.
In a skillet over medium heat, melt half of the butter. Add the diced onions and celery along with a generous pinch of kosher salt. Sauté for 5 minutes, until softened and fragrant.
Add 2 more tbsp of the butter, then add the garlic, all of the herbs, salt and pepper. Season with another generous pinch of kosher salt. Sauté for 2-3 minutes until the garlic is fragrant. Adjust the heat to low.
Place a large sauce pan on another burner on medium high heat. Pour the chicken broth into the sauce pan. Let it heat for 2-3 minutes, just before boiling. Add the cream cheese and whisk until the chicken broth is creamy. Once combined, taste the mixture and add salt if needed.
Transfer the broth mixture to the onion/celery mixture and stir together over medium heat, until thoroughly combined. Turn off the heat.
Pour the baguette pieces into a large mixing bowl.
Add the creamy herb mixture to the bread. Toss together, then toss with the eggs.
Pour half of the bread mixture into a buttered 9 x 13 baking dish. Too with half of the brie cubes.
Add the rest of the bread mixture on top. Top with the remaining brie cubes. Drizzle one tbsp of melted butter on top for that golden brown perfection. Cover with foil and bake for 20 minutes.
Adjust the heat to 400 degrees. Remove the foil and bake for another 15 minutes uncovered. Serve immediately.