Creating Celery Gratin is easy and rewarding when you follow these simple steps:

1. Preheat Your Oven: Preheat your oven to 375°F (190°C).
2. Prepare the Celery: In a large pot, bring salted water to a boil. Add the celery pieces and blanch for about 5 minutes. Drain and set aside.
3. Make the Roux: In a medium saucepan, melt the butter over medium heat. Add the flour, whisking continuously for about 1 minute until it forms a paste.
4. Add Milk: Gradually pour in the milk while whisking to avoid lumps. Continue cooking until the mixture thickens, about 3-5 minutes.
5. Add Cheese: Stir in 3/4 cup of the shredded cheese until melted and smooth. Season with garlic powder, salt, black pepper, and paprika if using.
6. Combine: In a large mixing bowl, combine the blanched celery with the cheese sauce. Stir to coat evenly.
7. Transfer to Baking Dish: Pour the celery mixture into a greased 9×9-inch baking dish or similar sized casserole dish.
8. Prepare Topping: In a small bowl, mix the remaining cheese with the breadcrumbs. Sprinkle this mixture evenly over the celery.
9. Bake: Place the dish in the preheated oven and bake for 25-30 minutes or until the top is golden brown and bubbly.
10. Garnish: Remove from the oven and let it cool for a few minutes. Garnish with fresh parsley if desired.

By following these steps, you’ll have a delicious Celery Gratin that’s sure to impress!