To begin, cook the diced onion, diced green bell pepper, and Italian sausage together in a Dutch oven over medium heat. As the meat cooks, break it up with your spoon.
When the meat is browned and the onion & pepper are tender, (about 5 minutes) drain off any excess grease if necessary.
Add in the tomato sauce, tomato paste, beef broth, basil, marjoram, oregano, black pepper, and red pepper flakes. Stir these all together.
Bring this to a gentle boil, reduce the heat to low and simmer for 10 minutes.
Add in the mushrooms, pepperoni, and olives. Cook for 5 more minutes, or until the mushrooms are just tender.
Serve the stew with shredded Parmesan (or mozzarella) cheese and crackers.
Enjoy!
Notes
If you are making this for little kids, you can leave out the red pepper flakes if you feel it will be too spicy for them.