01 - Set oven to 350°F.
02 - Boil egg noodles in a large pot of salted water according to package directions until al dente. Drain and return to pot.
03 - Whisk together cream of mushroom soup and milk in a mixing bowl until smooth.
04 - Add drained tuna, frozen peas, and the soup mixture to the noodles. Fold gently until evenly combined.
05 - Transfer mixture to a lightly greased 2-quart casserole dish.
06 - Sprinkle breadcrumbs and shredded cheddar cheese evenly over the casserole if using. Bake uncovered for 20 minutes, or until hot and bubbling.
07 - Allow casserole to stand for 5 minutes before portioning and serving.