Preheat oven to 350 degrees F
Bring large pot of lightly salted water to a boil. Add egg noodles and cook 8-10 minutes until al dente, drain
Add oil in a skillet over medium heat. Add onion, celery, and salt/pepper to taste; cook for 3-5 minutes. Add garlic and cook for 2 more minutes, remove vegetables from heat and set aside
In a separate large skillet over medium-low heat, melt 1/2 cup butter. Sprinkle flour into melted butter and whisk constantly for 1 minute or until smooth. Increase heat to medium-high and gradually whisk in milk until combined. Whisking constantly, cook until sauce is bubbly, smooth and slightly thickened, about 3-5 minutes; remove from heat
Season roux sauce with salt and pepper to taste. Stir in the tuna, peas, cooked vegetable mixture, and cooked noodles.
Transfer to medium baking dish and top with crushed potato chips. Bake in preheated oven 20-30 minutes