Cut 1/2 the pepperoni slices into 4 pieces, set aside.
Heat a dutch oven or deep pot over MED HIGH heat. Add drizzle of olive oil and brown Italian sausage, crumbling it with a wooden spoon or potato masher as it cooks, about 4-5 minutes. Drain excess grease and return to pan.
Add cut pepperoni pieces, diced onion, and diced green pepper, and cook until softened, about 3 minutes. Add garlic and cook another 30 seconds, or until fragrant.
Stir in marinara sauce, oregano and basil. Add water, stir and bring to a boil over HIGH heat. When boiling, add pasta, stir, reduce to a simmer, cover with lid and simmer about 12-15 minutes, until pasta is tender and most of the liquid is gone.
Stir in 1 cup of mozzarella cheese, remove from heat. Taste and add salt and pepper as needed. Sprinkle top with remaining mozzarella, and lay remaining slices of pepperoni on top.
Broil on HIGH for 1-3 minutes, until cheese is bubbly, melted and slightly golden. Serve garnished with minced parsley or basil.