Preheat the oven to 350 F. Cook the egg noodles until al dente in a large pot of salted boiling water according to package instructions. Rinse with cold water, drain, and set aside.
In a large bowl, mix the cooked noodles, condensed cream of mushroom soup, milk, tuna, shredded cheese, frozen peas, chopped onion, garlic powder, and pepper until well combined.
Make the crunchy topping: in a small bowl, mix the panko breadcrumbs with the melted butter until well combined.
Spoon the mixture into a 9x13-inch casserole dish and top evenly with the breadcrumb mixture.
Bake for 20 minutes or until the panko breadcrumbs are golden and crispy.