Preheat the oven to 400°F (200°C).
Place the hot cooked egg noodles in a 3-quart casserole dish. Add the condensed cream of mushroom soup, drained tuna, frozen peas, and milk. Stir thoroughly until the ingredients are evenly combined and coated with the creamy sauce.
Transfer the casserole dish to the preheated oven and bake for approximately 30 minutes, or until the mixture is thoroughly heated and bubbling.
Remove the dish from the oven and stir the casserole well to redistribute the sauce evenly throughout the noodles and filling.
Combine the dry bread crumbs and melted butter in a small bowl, mixing until the crumbs are evenly coated.
Scatter the buttered bread crumbs uniformly across the surface of the hot casserole. Return the dish to the oven and bake for an additional 5 minutes, or until the topping becomes crisp and golden brown.
Remove the casserole from the oven and allow it to cool for a few minutes before serving.