Preheat the oven to 350°F (175°C).
Cook the egg noodles according to package instructions until al dente. Drain and set aside.
In a large mixing bowl, combine the condensed cream of mushroom soup, Velveeta cheese cubes, and milk. Microwave in 30-second intervals, stirring between each, until the Velveeta is completely melted and the mixture is smooth.
Add the drained tuna, thawed peas, chopped onion, black pepper, and garlic powder to the cheese mixture. Stir until well combined.
Fold the cooked egg noodles into the tuna and cheese mixture until evenly coated.
Transfer the mixture to a greased 9×13-inch baking dish.
In a small bowl, mix the crushed potato chips with the melted butter.
Sprinkle the shredded cheddar cheese evenly over the casserole, then top with the buttered potato chips.
Bake in the preheated oven for 25 to 30 minutes, or until the casserole is bubbly and the topping is golden brown.
Remove from the oven and let it cool for 5 minutes before serving.