Preheat your oven to 375°F. Grease a 9x13-inch baking dish with butter or cooking spray.
Cook the egg noodles according to package directions until al dente. Drain well and set aside.
In a large bowl, combine the cream of mushroom soup, milk, tuna, frozen peas, and half the cheddar cheese. Mix well and season with salt and pepper.
Add the cooked noodles to the bowl and stir everything together until well combined. Pour the mixture into your prepared baking dish.
In a small bowl, mix the breadcrumbs with melted butter. Sprinkle the remaining cheese over the casserole, then top with the buttered breadcrumbs.
Bake for 25-30 minutes, or until the casserole is bubbly and the topping is golden brown. Let it rest for 5 minutes before serving.