1. Preheat oven to 375°F; grease an 11-by-7-inch baking dish.
2. Melt butter in a pan over medium-high heat. Whisk in flour, 2 minutes. Whisk in milk and broth. Cook, stirring, until mixture becomes thick and smooth, about 10 minutes. Season with salt and pepper.
3. Bring a pot of salted water to a boil. Cook noodles for 5 minutes. Drain; return to pot. Stir in sauce, tuna and peas. Spread evenly in baking dish.
4. Mix bread crumbs and cheese; sprinkle over baking dish. Drizzle with oil. Bake 20 to 25 minutes.