Preheat oven to high-broil.
In a large oven-proof skillet or pot, add Italian sausage and ¼ cup water and cook 4-5 minutes, until liquid is completely cooked out.
Add olive oil, diced onions, mushrooms and garlic, cook 5 minutes.
Then add tomato sauce, water, Italian seasoning pasta, and pepperoni; season with salt and pepper, to taste.
Bring to a boil; cover, reduce heat to medium and simmer until pasta is cooked through, about 12-14 minutes. Stir every 3-4 minutes, if needed add a ¼ cup water half way through, so that you don’t burn the pasta to the bottom.
Remove from heat; top with mozzarella and parmesan cheese.
Place into oven and cook until melted and golden brown, 3-5 minutes.
Remove from oven, top with freshly chopped parsley and serve!