Preheat your oven to 375°F (190°C).
In a large pot, cook spaghetti according to package instructions. Drain and return to the pot. Stir in marinara sauce until well coated.
In a small bowl, combine melted butter with minced garlic and dried herbs. Mix well.
Slice each piece of Italian bread in half lengthwise, creating a top and bottom piece.
Squeeze a little of the garlic butter mixture onto the inside of each half of the bread.
Place a generous amount of the spaghetti mixture on the bottom half of each piece of bread. Top the spaghetti with a handful of shredded mozzarella cheese.
Place the top half of the bread over the cheese. Brush the remaining garlic butter on top of the bread.
Place the stuffed bread on a baking sheet. Optionally, cover with aluminum foil for a softer crust or leave uncovered for a crispier texture.
Bake in the preheated oven for 15 minutes. If desired, remove the foil and bake for an additional 5-10 minutes until the cheese is bubbly and golden.
Remove from the oven, let cool for a few minutes, and then slice into pieces. Garnish with chopped fresh parsley if desired.