Preheat your oven to 350 degrees F and spray a 9x13 baking dish with non-stick cooking spray.

Prepare egg noodles by cooking them for two minutes less than the package instructions. Drain them well.

In a skillet, melt butter over medium heat. Add diced onions and cook until they are tender.

In a large bowl, combine cream of mushroom soup, mayonnaise, sour cream, milk, salt, pepper, and the cooked onions. Mix well.

Gently fold in the tuna, peas, and cheddar cheese into the mixture until combined.

Carefully fold in the prepared egg noodles, ensuring they are coated well with the mixture.

Pour everything into the prepared casserole dish and top with crushed potato chips.

Bake uncovered for approximately 30 minutes, or until heated through and bubbling.