Preheat oven to 375 degrees Fahrenheit.
Slice mushrooms and dice onions. Add olive oil in a large frying pan over medium heat. Once the oil is warmed, add the mushrooms and onions and sauté until the onions are translucent.
Add enough water in a stock pot and bring it to a boil. Add egg noodles and boil until al dente, or about 7 minutes.
Add mushroom soup, cream cheese, milk, and sour cream to the mushroom and onion mixture. Warm on the stovetop until heated through. Add salt and pepper to taste.
Transfer drained cooked pasta to the baking pan.
Add the mushroom sauce to the top of the pasta and mix well.
Drain the tuna and add the tuna into the mixture.
Top with shredded cheese.
Bake at 375 degrees Fahrenheit until the onions are golden brown. Serve hot and enjoy this classic recipe.