1Heat a large saute pan to med. Add butter and onion, cook till slightly translucent. Add cubed ham and cook for 2 mins. Add mushrooms, cook for another 2 mins. Remove from heat. Set aside.
2Im a large baking dish, put cooked pasta, soup, 1 cup of Cheddar and Jack cheeses and toss. Add onion, ham and mushroom mixture and mix well but carefully. You don't want to crush the pasta. Add the salt and pepper to taste.
3Smooth out top and sprinkle with remaining cheeses. Bake for 45 mins or until heated through and golden brown on top.