Brown sausage, onions, bell pepper and mushroom stems. Add salt, garlic powder and cayenne pepper. Add water and bring to a boil. Add rice and parsley. Cover and remove from heat. Let stand for 15 minutes. Meanwhile, blend mayonnaise and cheese. Combine half of mayonnaise mixture to all of cooked sausage-rice mixture. Stuff mushrooms with this and spoon remaining mayonnaise-cheese mixture on top of mushrooms. Place in 9 x 12-inch baking dish and bake at 350F for 35 minutes. Mushrooms will appear puffy and golden when done.