Fill a large pot with lightly salted water and bring to a rapid boil.
Add egg noodles and cook until tender yet firm to the bite, 7 to 9 minutes.
Drain the noodles in a colander.
Preheat the oven to 425 degrees F.
In a large mixing bowl, add noodles, condensed soup, 1 cup cheese, tuna, peas, mushrooms, and onion.
Mix until well combined.
Transfer the mixture into a 9×13-inch casserole dish.
Top with crushed potato chips and remaining 1 cup of cheese.
Bake until cheese is bubbly, about 15 to 20 minutes.
Notes
Tips and Tricks
Don't Overcook the Noodles - Cook the egg noodles just until tender. They'll continue cooking in the oven, so slightly undercooked noodles prevent a mushy casserole.Drain Your Ingredients Well - Make sure to drain the tuna and mushrooms completely. Extra liquid makes the casserole watery instead of creamy.Use Freshly Shredded Cheese - Shred your own cheese from a block instead of buying pre-shredded. It melts better and creates a creamier texture.Crush the Chips Fresh - Crush potato chips right before topping the casserole. They'll stay crispier during baking.Let It Rest - Allow the casserole to sit for 5 minutes after baking. This helps everything set and makes serving easier.Add Extra Flavor - Stir in garlic powder, black pepper, or a splash of Worcestershire sauce to boost flavor.
Storing and Reheating
Refrigerate - Store leftovers in an airtight container in the refrigerator for up to 3 days.Freeze - Wrap individual portions tightly in plastic wrap, then place in a freezer-safe container. Freeze for up to 2 months. Thaw overnight in the refrigerator before reheating.Reheat in Oven - Place a serving in an oven-safe dish, cover with foil, and warm at 350 degrees F for 15 to 20 minutes until heated through.Reheat in Microwave - Place a serving on a microwave-safe plate and heat on high for 1 to 2 minutes, stirring halfway through, until hot.