In a large saucepan, melt 2 tablespoons butter and blend in flour. Cook for 1 minute.
Gradually stir in milk, cook until thick. Add salt, pepper and cheese, stir until cheese melts. Set aside.
In a large skillet saute the ham and green onion in 3 tablespoons butter until onion is tender. Add eggs and cook over medium heat until eggs are set, stir in mushrooms and cheese mixture. Spoon into a greased 13 x 9 x 2 inch casserole dish.
Combine topping ingredients, sprinkle evenly over casserole.