Preheat your oven to 350˚F and grease a 13x9 casserole dish.

In a heavy-bottomed skillet, melt 2 tablespoons of butter over medium heat and brown the bread crumbs for about 5 minutes until golden and fragrant. Set aside to cool.

In a large skillet, sauté the diced celery, chopped onion, and fresh parsley in ½ cup of butter for about 5 minutes until softened. Stir in the cubed bread and season with salt, pepper, and poultry seasoning, tossing to combine.

Transfer the mixture to the greased casserole dish and drizzle with chicken broth.

In another large skillet, melt 1 cup of butter over medium-high heat. Whisk in the flour until well combined.

Gradually add the chicken broth and milk, whisking continuously to avoid lumps. Season with salt and cook over medium heat, stirring constantly for about 10 minutes until thickened.

Whisk the eggs in a small bowl and slowly add 1 cup of the hot broth mixture to the eggs, whisking to temper them.

Pour this egg mixture back into the remaining hot broth, cooking on low for another 3 minutes while stirring gently.

Pour the thickened broth mixture over the prepared bread cubes in the casserole dish. Layer the cooked chicken on top and sprinkle the browned bread crumbs evenly over everything.

Place the casserole in the preheated oven and bake for 30-35 minutes until bubbly and the center reaches 160˚F.