1 (10.75 ounce) can condensed cream of mushroom soup
3/4 cup whole milk
1 (5 ounce) can tuna
2 slices processed cheese food (such as Velveeta®)
1/2 cup crushed potato chips, or as needed
Bring a large pot of lightly salted water to a boil. Cook egg noodles in the boiling water, stirring occasionally until cooked through but firm to the bite, about 5 minutes. Drain.
Preheat oven to 350 degrees F (175 degrees C).
Combine mushroom soup, milk, and tuna in a saucepan over medium heat; cook until well blended and warmed through, about 5 minutes. Pour mixture into a 9x13-inch baking dish; add noodles and mix well. Top noodles with cheese food and sprinkle potato chips over cheese.
Bake in the preheated oven until casserole is bubbling, 30 to 45 minutes.