In a large pot with boiling salted water cook egg noodles until al dente. Drain.
In a large bowl combine the cooked egg noodles, cream of mushroom soup, evaporated milk, tuna, grated American cheese, and chopped onion. Pour into a greased 1.5 quart casserole dish. Sprinkle the top with the crumbled potato chips and the paprika.
Bake in a preheated 425 degree F (220 degree C) oven for 15 to 20 minutes.