Preheat your oven to 375°F (190°C). Lightly grease a 9x13 inch baking dish.

Bring a large pot of salted water to a boil. Add the egg noodles and cook according to package directions until al dente (slightly firm). Drain well and set aside.

In a medium saucepan, melt the butter over medium heat. Add the diced celery and onion, and sauté for 3-5 minutes until softened but not browned.

Sprinkle the flour over the vegetables and cook, stirring constantly, for 1 minute to create a roux.

Gradually whisk in the milk until smooth. Bring the mixture to a gentle simmer, stirring constantly, until it begins to thicken. Stir in the condensed cream of mushroom soup, garlic powder, onion powder, salt, and pepper. Continue to cook for another 2-3 minutes, stirring, until the sauce is smooth and hot.

Remove the saucepan from the heat and stir in the sour cream until fully combined.

In a large mixing bowl, combine the cooked and drained egg noodles, drained tuna, frozen peas, and the sautéed celery and onion. Pour the creamy sauce over the mixture and gently fold everything together until all ingredients are evenly coated.

Transfer the tuna noodle mixture into the prepared 9x13 inch baking dish, spreading it evenly.

In a small bowl, combine the crushed potato chips and shredded cheddar cheese. Sprinkle this topping evenly over the casserole.

Bake for 25-30 minutes, or until the casserole is bubbly around the edges and the topping is golden brown and crispy. Let stand for 5-10 minutes before serving.