Cook the egg noodles in a pot of salted boiling water until just tender. Drain and set aside.
While the noodles are cooking, melt the butter in a large non stick pan on medium heat, when hot, add the onion and cook until tender.
Add the soup, milk, and cheese. Stir together and heat through.
Preheat your oven to 190° C (375° F), get out and grease a 2 quart casserole.
Return the cooked noodles to the pot they were cooked in, then add the soup mixture from the pan and stir together.
Add the tuna, mushrooms, ½ cup sliced black olives, 2 tablespoons parsley, and lemon juice. Mix together.
Pour mixture into the prepared casserole. Sprinkle with additional Parmesan as desired. Sprinkle with paprika as desired.
Bake for 20-25 minutes.
Top with additional parsley and sliced black olives.
Serve and enjoy.