Par boil Manicotti noddles 2-3 Minutes and run under cold water immediately to stop cooking. Brown meat and onion. In a bowl mix meat and onion with all ingredients, adding half of the Mozzarella cheese cubed to the mixture. Using a teaspoon, stuff the Manicotti noodles. Spread some Marinara sauce on the bottom of a lasagna pan, place stuffed noodles in pan, top noodles with the remainder of Marinara sauce, some sliced mushrooms, then the remainder of the Mozzarella cheese. Cook at 350 for 30 Minutes or until cheese is melted. You can substitute chicken for ground meat.