Clean and trim the mushrooms and cut into thin slices. Put the oil, garlic, chopped parsley and mushrooms into a saucepan and cook over a moderate heat, stirring and turning occasionally, for 10-12 minutes. Cut the ham and cheese into small dice. Cook the pasta until al dente, drain well and stir in the mushrooms, ham and mozzarella. Transfer to a buttered ovenproof dish and place in a preheated hot oven (500 F) until thecheese begins to melt and the pasta has browned a little.