Brown ground beef and sausage, drain, and set aside. In a large pot, heat olive oil over medium heat. When the oil is hot, add the onions and sauté until soft and translucent, about 5 minutes. Add the garlic and cook for about 1 minute. Next add the bell pepper, mushrooms, diced tomatoes, tomato sauce & paste, spices, ketchup, chicken stock and bring to a boil. Reduce heat to low, cover and simmer for one hour.
Preheat oven to 350F. Cook jumbo shells according to box directions. Drain shells and let cool until they are able to handle. Stuff the shells with Mozzarella & sharp cheese and place in baking dish. Spoon the meat sauce over the shells and top with a little more cheese. Cover dish with tin foil and bake in oven for 30 minutes. Remove foil and bake for another 15 minutes. Top shells with parmesan cheese and parsley.