Preheat oven to 400°F. Spread 1 cup of marinara sauce evenly on the bottom of a casserole or baking dish.
Brown the sausage in a frying pan over medium heat, breaking into small pieces. Tip: Use a potato masher to easily create fine pieces of sausage.
Wash and dry the banana peppers. Slice them down the center, leaving 1/2 inch uncut on each end. Use a spoon to scrape out seeds and ribs.
In a large mixing bowl, combine ricotta cheese, parmesan cheese, egg, dried parsley, 1.5 cups mozzarella cheese, and browned sausage.
Stuff each pepper generously with the mixture and place in the casserole dish.
Drizzle remaining cup of marinara sauce over the stuffed peppers. Cover with foil and bake for 40 minutes.
After baking, carefully remove foil and sprinkle remaining 1/2 cup of mozzarella on top of peppers. Bake for another 10 minutes or until cheese is melted.