Preheat over to 350F degrees.
Cook spaghetti according to package directions in salted water.
8 ounces spaghetti
Melt butter in a large skillet. Add onion and mushrooms and cook until onion is soft and mushrooms are browned.
2 Tablespoons butter, 1/2 medium onion, 6 ounces mushrooms
Add soup, milk, salt and pepper to the skillet and mix well.
1 (10.75 ounces) can condensed cream of chicken soup OR cream of mushroom soup, 1/2 cup milk, ½ teaspoon salt, 1/4 teaspoon black pepper
Add ham, peas, ¾ cup cheddar cheese, and Parmesan cheese and stir and cook over medium heat until cheese is melted. Season to taste with salt.
1 1/2 cups diced ham, 1 cup frozen peas, 1 cup shredded cheddar cheese, 1/4 cup shredded Parmesan cheese
Add drained pasta to the pan and mix well.
Add to a casserole dish and sprinkle with remaining cheddar cheese
Bake, uncovered, for 20-25 minutes or until bubbly.
Serve immediately.